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ASSOCIATION OF STRUCTURAL ENGINEERS 
OF THE PHILIPPINES, INC. 



NATIONAL 
STRUCTURAL 
CODE OF THE 
PHILIPPINES 
2015 



VOLUME I 

BUILDINGS, TOWERS, AND OTHER 
VERTICAL STRUCTURES 








PREFACE TO THE NSCP VOLUME 1, SEVENTH EDITION, 2015 


Introduction 


ASEP recognizes the need for an up-to-date structural code addressing the design and installation of structural systems 
through requirements emphasizing performance. The new National Structural Code of the Philippines (NSCP Volume I) is 
designed to meet these needs through various model codes/regulations, generally from the United States, to safeguard the 
public health and safety nationwide. 


This' updated Structural Code establishes minimum requirements for structural systems using prescriptive and 
performance-based provisions. It is founded on broad-based principles that make possible the use of new materials and 
new building designs. Also, this code reflects the latest seismic design practice for earthquake-resistant structures. 


Changes and Developments 

In its drive to upgrade and update the NSCP, the ASEP Codes and Standards Committee initially wanted to adopt the latest 
editions of American code counterparts. However, for cases where available local data is limited to support the upgra e, 
then some provisions and procedures of the NSCP 7'" edition were retained. 

This NSCP 7th edition is referenced from the following: 

a. Uniform Building Code UBC-1997 

b. International Building Code IBC-2009 

c. American Society of Civil Engineers ASCE/SEI 7-10 

d. American Concrete Institute ACI3 1 8- 1 4M 

e. American institute for Steel Construction AISC-05 with Supplementary Seismic Provisions 

f American Iron and Steel Institute AIS1 S 1 00-2007 

g. Reinforced Masonry Engineering Handbook of America 

h. Concrete Masonry Handbook, 6th Edition 

i. American National Standard Institute ANSI E1A/TIA-222-G-I-2007 

j. American Society for Testing and Materials (ASTM) Standards 


Significant revisions are summarized as follows: 

a. Chapter 1 — General Requirements 

The changes made in this chapter are the following: 
a. 1 Section 1 02 - Definition of Failure 
a.2 Section 1 03 - Classification of Structures 

School buildings of more than one story, hospitals, designated evacuation centers, structures 
are under the essential facilities category. Section 104 - Design Requirements 

Churches, Mosque and other related religious structures are under the special occupancy 
category Section 104-Design Requirements. 

The provision for deflection of any structural member under the serviceability requirement is 
deleted. This requirement for concrete and steel is specified in Chapters 4 and 5 respectively. 

New requirements are added to the design review section. 

a.3 Section 105 - Posting and Instrumentation 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 

iv 


The provision of installed recording accelerograph is adjusted, 

a.4 Inclusion of Appendix 1-A : Recommended Guidelines on Structural Design Peer Review of 
Structures 2015 

a.5 Inclusion of Appendix 1-B: Guidelines and Implementing Rules on Earthquake Recording 
Instrumentation for Buildings 


b. Chapter 2 - Minimum Design Loads 

The changes made in this chapter are the following: 

b. 1 Section 203 - Combination of Loads 

The load factors and load combinations are revised particularly the load combinations 
including wind load. 

b.2 Section 205 - Live Loads 

Additional loads are incorporated in the table for minimum uniform and concentrated loads 
particularly the parking garage and ramp live load. 

b.3 Section 207 - Wind Loads 

Wind load provisions, which were previously based on ASCE7-05, are updated based on 
ASCE7-10. In this edition, three different wind contour maps for the entire Philippine 
archipelago are generated and provided for determining the basic wind speeds for different 
categories of building occupancies as defined in Table 103-1. These maps provide basic wind 
speeds that are directly applicable for determining pressures for design strength. Strength 
design wind load factor is 1.0; whereas, allowable stress design wind load factor is 0.6. 
Generally, basic wind speeds correspond to 3%, 7% and 15% probability of exceedance in 50 
years (MRI = 1700,700 and 300 years, respectively). Four (4) permitted procedures in 
determining the design wind loads for main wind-force resisting systems (MWFRS), for other 
structures and building appurtenances and for components and cladding (C&C) are provided 
such as; 

® directional procedure for buildings of all heights, 

© envelope procedure for low-rise buildings, 

© directional procedure for other structures and building appurtenances and 
analytical procedure for components & cladding, and 
© wind tunnel procedure 

The ANSI EIA/TIA-222-G-2005 and ANSI EIA/TIA-222G-1-2007 are now fully referenced 
for computing wind loads on steel antenna towers and antenna supporting structures. 

b. 4 Section 208 - Earthquake Loads 

The near-source factors for 2-km distance from a causative fault is included in addition to 5- 
km, 10-km, 15-km distance and beyond 15-km distance. 

ASCE/SEI 7-10, using spectral acceleration, is recognized as an alternative procedure in the 
determination of the earthquake loads. 

c. Chapter 3- Earthworks and Foundations 

The revisions made in this chapter are the following: 

c. 1 Provisions pertaining to the conduct and interpretation of foundation investigations for cases 

involving liquefiable, expansive or questionable soils are adopted; 


National Structural Code of the Philippines Volume l, 7th Edition, I s * Printing, 2016 

v 


c.2 The section on footings is amended to incorporate provisions for differential settlement, 
design loads and vibratory loads; 

c.3 The section on pile foundations is amended to incorporate new provisions on splicing of 
concrete piles; and 

c.4 The section on special foundations, slope stabilization and materials of construction are added. 

c.5 Provisions for construction in Zone 4 pertaining to reinforcement of Precast Prestressed Piles 
have been revised to ensure consistency with ACI 318. 

c.6 The figure for cut slopes has been amended for clarity; 

c.7 The figure for fill slopes has been amended for clarity and some provisions have been 
modified; 

c.8 A table on the minimum required number of boreholes has been added to the section on 
foundation investigation; 

c.9 Provisions pertaining to minimum dimensions of ditches have been modified; 

c. 10 The section on excavations and fills has been amended to incorporate provisions for scouring 
and erosion protection as well as support of excavations and open cuts; 

c. 1 1 Provision pertaining to general pile requirements have been expand to include design of piles 
and pile groups subjected to lateral loads. 

c.12 A Section on MSE Structures and Similar Reinforced Embankments and Fills has been added. 
Chapter 4 - Structural Concrete 

To reflect the reorganization of ACI 318-14 which contained a number of significant technical changes, the 
ASEP adopted similar changes in the NSCP 2015 7th Edition. The latest ACI 3 18 was reorganized as a member- 
based document, i. e., particular member type, such as beam, column, or slab will have separate sub-sections for 
all requirements to design that particular member type. This will eliminate the need to flip through several 
Sections to comply with all the necessary design requirements for a particular structural member, as was 
necessary with the old organization format. 

d.l Section 401: General 

General information regarding the scope and applicability of NSCP 2015, Vol. 1 is provided. Additional sub- 
section on interpretation is included to help users better understand Chapter 4, Structural Concrete. 

d.2 Section 402: Notation and Terminology 

The definition for hoops has been modified because the use of interlocking headed bars is a concern regarding 
the possibility that it will not be adequately interlocked and because the heads could become disengaged under 
complex loadings well into the non-linear range of response. It is now defined as a closed tie oi continuously 
wound tie, made up of one or several reinforcement elements, each having seismic hooks at both ends. 

A definition for special seismic systems, a term used in Sections 418 and 419, has been added. 

d.3 Section 403: Referenced Standards 

The following referenced specifications have been added to Section 403.2.4: 

* ASTM A370-14, Standard Test Methods and Definitions for Mechanical Testing of Steel Products 
© ASTM A 1085- 13, Standard Specification for Cold-Formed Welded Carbon Steel Hollow 
Structural Sections (PISS) 

o ASTM C173/C173M-14, Standard Test Method for Air- Content of Freshly Mixed Concrete by 
Volumetric Method 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



* ASTM C1582/CI582M-1 1, Standard Specification for Admixtures to Inhibit Chloride- 
Induced Corrosion of Reinforcing Steel in Concrete 

A new referenced specification from Australia and New Zealand, Section 403.2.6 is added. These 
standards were included as ACI 3 1 8 has no provisions related to Qualifications on the Use of Quenched 
Tempered QT/Thermo-Mechanically Treated Reinforcement, which are the type manufactured, sold, 
and commonly used for building construction in the Philippines: 

© AS/NZS 4671: 2001, Steel Reinforcing Materials 

© NZS 3101: 2006, Part 1 and Part 2, Concrete Structures Standard, and Design of 
Concrete Structures 

© NZS 3 1 09, Amendment 2, Welding of Reinforcing Steel 
© AS/NZS 1554.3: 2008, Part 3, Structural Steel Welding of Reinforcing Steel 

The following referenced specifications have been deleted: 

© ASTM C109/C109M-08, Standard Test Method for Compressive Strength of Hydraulic 
Cement Mortars (Using 50 mm Cube Specimens) 

© ASTM Cl 92/Cl 92M-07, Standard Practice for Making and Curing Concrete Test 
Specimens in the Laboratory 


Several referenced standards and specifications have been updated, as in most cases with every edition 
of the NSCP. Note that the edition of every referenced standard is important. The NSCP does not 
necessarily adopt new editions of referenced standards unless they are vetted before the publication of 
each edition of the standard. 

d.4 Section 404: Structural System Requirements 

This new Section has been added to Chapter 4 to introduce structural system requirements. 
This Section contains Sub-sections on Materials, Design Loads, Structural System and Load 
Paths, Structural Analysis, Strength, Serviceability, Durability, Sustainability, Structural 
Integrity, Fire Resistance, Requirements for Specific Types of Construction, Construction and 
Inspection, and Strength Evaluation of Existing Structures. Most of these Sub-sections refer to 
the other Sections in the NSCP. The Sub-section on construction and inspection, for instance, 
refers to Section 426. In the areas for Sustainability and Fire Resistance, the NSCP does not 
have specific requirements. This Sub-section on Sustainability allows the licensed design 
professional to specify in the construction documents, sustainability requirements in addition 
to the strength, serviceability, and durability requirements of the NSCP. The strength, 
serviceability, and durability requirements are required to take precedence over sustainability 
considerations, though these requirements are generally in harmony with sustainable 
structures. In the Sub-section on Fire Resistance, the NSCP refers to the fire-protection 
requirements of the NSCP Chapter 4, Sub-section 420.6.1. However, if the National Building 
Code of the Philippines requires a greater concrete cover, such greater thickness shall govern. 

d,5 Section 405: Loads 

The following modification has been made in the provision for live load reduction because 
there are still unincorporated areas where there may not be included in the previous editions of 
the NSCP. The 7 l)1 Edition, Sub-section 405.2.3 - Live load reductions shall be permitted in 
accordance with the National Building Code of the Philippines, or in its absence, in 
accordance with ASCE/SEI 7. 

For many Code revision cycles, ACI 318 retained provisions for service-level earthquake 
forces in the design load combinations. In 1993, ASCE/SEI 7 converted earthquake forces to 
strength-level forces and reduced the earthquake load factor to 1.0, and the model building 

National Structural Code of the Philippines Volume 1, 7th Edition, 1 st Printing, 2016 

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codes followed suit. In modern building codes around the world, earthquake loads are now 
strength-level forces. Any references to service-level earthquake forces have been deleted. 


d.6 Section 406: Structural Analysis 

The following new item has been added in Sub-section 406.6.2.3: 

(b) For frames or continuous construction, it shall be permitted to assume the intersecting membei 
regions are rigid. 

Previous NSCP 6 th Edition has been silent on the use of finite element analysis (FEA), though it is now 
frequently used. Sub-section 406.9 now has provisions that are intended to explicitly allow the use of 
FEA and to provide a framework for the future expansion of FEA provisions, but not as a guide toward 
the selection and use of FEA software. The new Sub-section on diaphragms and collectors makes 
explicit reference to the use of FEA, which makes it imperative that the NSCP 7'” Edition recognize the 
acceptability of its use. 
d.7 Section 408: Two-Way Slabs 

Sub-section 418.10.1 (corresponding to ACI 318M-1 1, Section 18.9.1), says that a minimum 
area of bonded reinforcement shall be provided in all flexural members with unbonded 
prestressing tendons. The purpose of the minimum unbonded reinforcement over the tops of 
columns is to distribute cracking caused by high local flexural tensile stresses in areas ol peak 
negative moments. However, the high local flexural tensile stresses are not unique to slabs 
with unbonded tendons. The new reorganized Sub-section 408.6.2.3 (corresponding to ACI 
318M-14 Section S.6.2.3) requires the same minimum reinforcement in slabs with unbonded 
or bonded tendons, except that the area of bonded tendons is considered effective in 
controlling cracking. 

It was also decided by the ACI 318 Committee, that if the same bonded reinforcement were 
required for both bonded and unbonded post-tensioned two-way systems, the structural 
integrity requirements for both systems should also be the same. The structural integrity 
requirements in ACI 318M-11, Section 18.12.6 applied to two-way post-tensioned slab 
systems with unbonded tendons only. The structural integrity requirements in ACI 318M-14 
Section 8. 7.5.6 (corresponding to the NSCP 2015, Sub-section 408.7.5.6) now apply to two- 
way post-tensioned slab systems with bonded as well as unbonded tendons. 

d.8 Section 409: Beams 

The use of open web reinforcement for torsion and shear in slender spandrel beams by the 
precast concrete industry as an alternative to the closed stirrups traditionally mandated by this 
Code. Eliminating closed stirrups is desirable because they cause reinforcement congestion, 
production costs also increase significantly because pre-tensioning strand must be threaded 
through the closed stirrups. 

A new relevant Sub-section 409.5.4.7 for solid precast sections is added to the NSCP 7 ,h 
Edition. 

d.9 Section 412: Diaphragms 

For the first time, a new Section 412, added design provisions for diaphragms in buildings 
constructed in areas of low seismicity (Zone 2) The new Section applies “to the design of non- 
prestressed and prestressed diaphragms, including: 

(a) . Diaphragms that are cast-in-place slabs 

(b) . Diaphragms that comprise a cast-in-place topping slab on precast elements 

Association of Structural Engineers of the Philippines, Inc. (ASEP) 

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(c) . Diaphragms that comprise precast elements with end strips formed by either a cast- 
in-place concrete topping slab or edge beams 

(d) . Diaphragms of interconnected precast elements without cast-in-place concrete 
topping 

d.10 Section 418: Earthquake-Resistant Structures 

There are a number of significant and substantive changes to this Section. 

Column confinement - The ability of the concrete core of a concrete reinforced column to sustain compressive 
strains tends to increase with confinement pressure. Confinement requirements for columns of special moment 
frames, and for columns not designated as part of the seismic-force-resisting system in structures assigned to 
seismic zone 4 (similar to ASCE 7-10 Seismic Design Categories D, E, and F), with high axial load or high 
concrete compressive strength are significantly different. 

Transverse reinforcement - One important new requirement for special moment frame columns are included in 
Sub-sections 418.7.5.2 and 418.7.5.4. There are new restrictions on the use of headed reinforcement to make up 
hoops. 

Special moment frame beam-column joints - For beam-column joints of special moment frames, clarification of 
the development length of the beam longitudinal reinforcement that is hooked, requirements for joints with 
headed longitudinal reinforcement, and restrictions on joint aspect ratio are new. For beam-column joints of 
special moment frames, clarification of development length of beam longitudinal reinforcement that is hooked, 
requirements for joints with headed longitudinal reinforcement, and restrictions on joint aspect ratio are new. 

Special shear walls - Subsection 418.10 (equivalent to AC1 31S-14M-14 Section 18.10, previously 
ACI 318M-11 Section 21.9), has been extensively revised in view of the performance of buildings in the Chile 
earthquake of 2010 and the Christchurch, New Zealand, earthquakes of 201 1, as wells as full-scale reinforced 
concrete building tests. In these earthquakes and laboratory tests, concrete spalling and vertical reinforcement 
buckling were at times observed at wall boundaries. 

For ASTM A615 Grade 420 bars used as longitudinal reinforcement in special moment frames and special shear 
wails, the NSCP 7 lh Edition now requires the same minimum elongation as ASTM A706 reinforcement. 

d.ll Section 419: Concrete: Design and Durability Requirements 

Quite a few changes have been made in concrete durability requirements, which are now located in this Section. 

d.12 Section 420: Steel Reinforcement Properties, Durability and Embedments 

The definition of yield strength of high-strength reinforcement for Grade 420 (Grade 60) in this Section is now, 
for the first time, the same as that in ASTM specifications, except for bars with less than 420 MPa, the yield 
strength shall be taken as the stress corresponding to a strain of 0.35 percent. 

Delormed and plain stainless steel wire and welded wire conforming to ASTM A 1 022 is now permitted to be 
used as concrete reinforcement. 

Sub-section 420.2.2.5 requires “Deformed non-prestressed longitudinal reinforcement resisting earthquake 
moment, axial force, or both, in special moment frames, special structural walls, and all the components of 
special structural walls including coupling beams and wall piers” to be ASTM A706 Grade 420 (Grade 60), 
ASTM 615 Grade 275 (Grade 40) or Grade 420 (Grade 60) reinforcement is permitted if two supplementary 
requirements are met, which are already part of the ASTM A706 specification. A third supplementary 
requirement is now added for ASTM A615 (Grade 60) reinforcement to be permitted for use in special moment 
frames, special structural walls. The minimum elongation in 200 mm (8”) must now be the same as that ASTM 
A615 (Grade 60) reinforcement. 

One aspect of the Code compliance that the Association of Structural Engineers of the Philippines is cautioning 
Designers and Constructors alike, is the introduction of ASTM 615 Grade 520 (Grade 75) in the Philippine 

National Structural Code of the Philippines Volume 1, 7th Edition, 1 st Printing, 2016 

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market. Since this was not covered by previous editions of the NSCP Vol. 1, it creates an impression of an 
unregulated use of a new high-strength reinforcement grade. NSCP 7 1 Ed.t.on, 

To put it clearly, Sub-section 420.2.2.5, corresponding to ACI 3 18M-14 Section 20.2.2.5, specifies the 
use of deformed non-prestressed longitudinal reinforcement resisting earthquake-induced moment, 
axial force, or both, in special moment frames, special structural walls, and all components of special 
structural walls, including coupling beams, and wall piers which shall be in accordance with (a) or (b): 

(a) . ASTM A706M, Grade 420 

(b) . ASTM A615M, Grade 280 

There was no mention that ASTM A615M, Grade 520, was allowed, although the use of micro-alloyed 
high-strength reinforcement may be allowed in the future through the issuance of a new ASTM or 
updated standard, and with proper validation by the Department of Trade and Industry s Bureau ot 
Standards. It will be premature to allow its use for special moment frames, special structural walls, and 
all components of special structural walls, including coupling beams, and wall piers tor Buildings 
located in areas of high seismicity (zone 4). The same restrictions indicated in Sub-section 420.7.6, on 
the use of quenched-tempered thermo-mechanically treated (QT/TMT) reinforcing bars in structures 
located in seismic zone 4 for Grade 420 reinforcement, shall also be applied to Grade 520, unless 
proven in subsequent studies and tests. 

d.13 Section 422: Sectional Strength 
The following are the changes in Section 422: 

For prestressed members, a new equation for the nominal axial strength at zero eccentricity has been 
introduced in Sub-section 422.4*2.3. 

New Sub-section 422.4.3*1, which requires that the nominal axial tensile strength of a non-prestressed, 
composite, or prestressed member, not to be taken greater than the maximum nominal axial tensile 
strength of member. 

d.14 Section 425: Reinforcement Details 

Two changes shown in Table 7 (part of Table 425. 3.2) are made to eliminate the differences between 
the required tail extension of a 90-degree or 135- degree standard hook, subject to a minimum of 75 
mm (3”). 

Mechanical or welded splices with strengths below 125% of the yield strength ol the spliced reinfoicing 
bars are no longer permitted. The associated stagger requirements have been deleted. Thus there is no 
longer a need to specify “full” mechanical or “full’ welded splices. 

d.15 Section 426: Construction Documents and Inspection 

In this section, the user will probably require some time to get used to, it starts with the following: 

426.1.1 This Sub-section addresses (a) through (c): 

(a) Design information that the licensed design professional shall specify in the construction 
documents, 

(b) Compliance requirements that the licensed design professional shall specify in the 
construction documents, 

(c) Inspection requirements that the licensed design professional shall specify in the 
construction documents. 

Thus, construction and inspection requirements have been consolidated, and they are now related to 
construction documents. The construction requirements are designated either as “design information” or 
“compliance requirements.” These are largely existing material that has been rearranged. The 

Association of Structural Engineers of the Philippines, Inc. (ASEP) 

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inspection requirements in Sub-section 426.13 are taken from Chapter 17 of the 2015 International 
Building Code (IBC) and were previously not part of ACI 318. 

Provisions in ACI 318-11 and earlier editions, which explained basic statistical considerations 
in mixture proportioning, are no longer found in ACI 318-14. Instead, ACI 301-10, 
Specifications for Structural Concrete , is referenced. 

These are some other changes in the makeup of NSCP 2016 7 th Edition that should be noted: 

1 . There are two new Sections: Section 404, Structural System Requirements and 
Section 412, Diaphragms. 

2. Section 422, Structural Plain Concrete, now Section 414. 

3. Section 423, Anchoring to Concrete, is now Section 417, with no significant 
changes. 

4. Section 42 1 , Earthquake-Resistant Structures, now Section 418. 

5. Section 427, Strut-and-Tie Models is now Section 423, with no significant 
changes. 

6. Section 420, Strength Evaluation of Existing Structures, is now Section 427. 

7. Section 419, Shells and Folded Plates, is now Section 428. 

8. Section 424, Alternative Design Method, now Section 429, is adapted from 
earlier editions of the NSCP. 

9. Section 425, Alternative Provisions for Reinforced and Prestressed Concrete 
Flexural and Compression Members, and Section 426, Alternative Load and 
Strength Reduction Factors, have been discontinued. 

10. On the other hand. Section 416, Precast Concrete, and Section 418, Prestressed 
Concrete, no longer exist as separate entities. The provisions of these Sections 
are now spread over several of the new Sections. 

Sub-section 418.18, Requirements for post-tensioning ducts and grouting have also been removed as 
being outdated. The Commentary now provides specification guidance. 

e. Chapter 5: Structural Steel. 

ASEP adapted the American Institute of Steel Construction (AISC) 14th Edition in this updated 
Structural Steel code. The revisions made in this chapter are the following: 

e.l The entire Structural Steel chapters are streamlined placing all chapter definitions under one 
Definition heading, tables are immediately shown where they are first mentioned, figures drawn 
larger, equation are all in boldface, extraneous user notes are removed, essential in-text definitions 
italicized and in-text equation terms are written in boldface for easy reference. 

e.2 Change of headings and terms. 

501.3.5 Filler Metal and Flux for Welding to 501.3.5 Consumables for Welding 
510.10.3 Web Crippling to Web Local Crippling 

557.5 Special Fabrication Requirements. Weld tabs changed to Run-off tabs under 
Exception. 

A-6.3 Beams changed to Beams Bracing 

e.3 Creation of new subtopic. 

APPENDIX A -4 

National Structural Code of the Philippines Volume 1, 7th Edition, 1 st Printing, 2016 

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f. 


STRUCTURAL FIRE f 

A -4.2.3. 1 Thermal Elongation is created under A-4.2.3 Material Strengths at Elevated 

Temperatures 
APPENDIX A-6 

STABILITY BRACING FOR COLUMNS AND BEAMS 
A-6.4 Beam-Column Bracing 

SECTION 529 BUCKLING-RESTRAINED BRACED FRAMES (BRBF) 

A section 529.3 was created as heading for 529.3.1 and 529.3.2 

e.4 Revision in load factor 

5 10.8 Column Bases and Bearing on Concrete 

2010- n c =2.5(/(SD) 

2015: 0c = 0.65(LRFD) = 2. 31(4SD) 

e.5 Revision in equations 

B-5. QUALIFYING CYCLIC TESTS OF BUCKLING-RESTRAINED BRACES 
51 1.2.2c Branches with Axial Loads in K-Connections 


2010 : 


Q s =r l 


1 + 


0 , 24 /" 


•frH * 1 


(5M.2-7) Q z 


; 2015: 



0.24 Y 12 \ 

c IV-v’hJ 


(5H>7) 


APPENDIX A-3 - DESIGN FOR FATIGUE 
A-3.4 Bolts and Threaded Parts 

A, -$(</„ -9382 ) 2 At = f id b - 0-9382 P)* 

2010: 4 ; 2015: 

Chapter 6: Wood. 

The revisions made in this Chapter are the following: 

f.l Section 616 - Design Provisions and Equations: The NDS 2015 Chapter 3 is adopted 
almost in its entirety; 

f.2 Section 6 1 7 - Sawn Lumber: The NDS 20 1 5 Chapter 4 is adopted almost in its entirety; 

f.3 Section 618 - Structural Glued Laminated Timber: The NDS 2015 Chapter 5 is adopted 

almost in its entirety; 

f.4 Tables 619.1-3 and 6 1 9. 1 -4 are revised based on NDS 20 1 5; and 


f.5 Other Sections affected are adj usted accordingly. 


Chapter 7: Masonry 

The revisions made in this chapter are the following: 

g. 1 The specified yield strength of steel reinforcement is 420MPa instead of 413 MPa / 415 MPa; 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 

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g.2 Section 710.6.3 and Section 710.7.1 

10mm diameter instead ofNo.9 gage wire 

g.3 Section 713.9.1 

20mm diameter instead of 19-gage 
25 mm diameter instead of 24-gage 

3. Acknowledgment 

The ASEP Codes and Standards Committee are indebted to Philippine Institute of Volcanology and Seismology 
(PHIVOLCS) and to Dir. Renato V. Solidum, Ph. D. for his unselfish contribution specifically on Section 208 of 
this code. 

ASEP acknowledges the contribution of Dr. Teresito C. Bacolcol and Ms. Madeline Cabologan of PHIVOLCS for 
the seismic maps used in this code. 

ASEP acknowledges the contribution of Engr. Carlos M. Villaraza for his unselfish contribution on Chapter 2 
Seismic/Earthquake Chapter. 

The contributions of ASEP members and other users of this code who have suggested improvements, identified 
errors and recommended items are recognized. 


ASEP also acknowledges the contribution of the industry partners, companies and individuals, who continue to 
support ASEP’s numerous undertakings. 

The ASEP Codes and Standards Committee also acknowledge Arch. Avigaile Genota Riola who designs the covers 
of the NSCP Volume 1, 2010 Edition and NSCP Volume 1, 2015 Edition. 


National Structural Code of the Philippines Volume I, 7th Edition, 1 st Printing, 2016 

xiii 


Suite 713, Future Point Plaza Condominium 1 
112 Fanay Avenue, Quezon City, Philippines 1100 


Tel* No. : (+632) 410-0483 
Fax No* : (+632) 411-8606 
Email: aseponl in e@gmai I .com 
Website:http://ww\v*aseponline.org 



National Structural Code of the Philippines Volume ! ? 7th Edition, 2015 








CHAPTER 1 - General Requirements 1-1 

Table of Contents 

SECTION 101 

TITLE, PURPOSE AND SCOPE 

101.1 Special Foundation Systems 2 

101.2 Purpose 2 

101.3 Scope 

1 0 1.4 Alternati ve Systems 2 

SECTION 102 

DEFINITIONS 

SECTION 103 

CLASSIFICATION 

OF STRUCTURES 

103.1 Nature of Occupancy q 

SECTION 104 

DESIGN REQUIREMENTS 

104.1 Strength Requirement 7 

1 04.2 Serviceability Requirement 

104.3 Analysis 7 

1 04.4 Foundation Investigation g 

104.5 Design Review g 

SECTION 105 

POSTING AND INSTRUMENTATION 

105.1 Posting of Live Loads 

105.2 Earthquake-Recording Instrumentation 9 

SECTION 106 

SPECIFICATIONS, DRAWINGS AND CALCULATIONS 

1 06. 1 General * 9 

106.2 Specifications * „ . 9 

1 06.3 Design Drawings 9 

SECTION 107 

STRUCTURAL INSPECTIONS, TESTS AND STRUCTURAL OBSERVATIONS 10 

107.1 General jq 

107.2 Definitions jq 

107.3 Structural Inspector jq 

107.4 Inspection Program j j 

1 07.5 Types of Work for Inspection I \ 

107.6 Approved Fabricators j3 

107.7 Prefabricated Construction j 3 

107.8 Non-Destructive Testing 14 

1 07.9 Structural Observation j 5 

APPENDICES 

LA - Recommended Guidelines on Structural Design Peer Review of Structures 2015 IA-1 

LA - Guidelines and Implementing Rules on Earthquake Recording Instrumentation for Buildings IB-1 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


1-2 CHAPTER 1 - General Requirements 


iiiWiiM it# ; > \ 

IpilllPtiRPOSE AND SCOPE .11111) 

101.1 Special Foundation Systems 

These regulations shall be known as the National 
Structural Code of the Philippines 2015, Volume I, 7th 
Edition, and may be cited as such and will be referred to 
herein as ‘'Ibis code." 

101.2 Purpose 

The purpose of this code is to provide minimum 
requirements for the design of buildings, towers and other 
vertical structures, and minimum standards and guidelines 
to safeguard life or limb, property and public welfare by 
regulating and controlling the design, construction, 
quality of materials pertaining to the structural aspects of 
all buildings and structures within this jurisdiction. 

101.3 Scope 

The provisions of this code shall apply to the construction, 
alteration, moving, demolition, repair, maintenance and use 
of buildings, towers and other vertical structures within this 
jurisdiction. 

Special structures such as but not limited to single family 
dwellings, storage silos, liquid product tanks and 
hydraulic flood control structures, should be referred to 
special state of practice literature but shall refer to 
provisions of this code as a minimum wherever 
applicable. 

For additions, alterations, maintenance, and change in use 
of buildings and structures, see Section 108. 

Where, in any specific case, different sections of this code 
specify different materials, methods of construction or 
other requirements, the most restrictive provisions shall 
govern except in the case of single family dwellings. Where 
there is a conflict between a general requirement and a 
specific requirement, the specific requirement shall be 
applicable. 


101.4 Alternative Systems 

The provisions of this code are not intended to prevent the 
use of any material, alternate design or method of 
construction not specifically prescribed by this code, 
provided any alternate has been permitted and its use 
authorized by the Building Official (see Section 102). 

Sponsors of any system of design or construction not 
within the scope of this code, the adequacy of which had 
been shown by successful use and by analysis and test, 
shall have the right to present the data on which their 
design is based to the Building Official or to a board of 
examiners appointed by the Building Official or the project 
owner/developer. This board shall be composed ot 
competent structural engineers and shall have authority to 
investigate the data so submitted, to require tests if any, and 
to formulate rules governing design and construction of 
such systems to meet the intent of this code. These rules, 
when approved and promulgated by the Building Official, 
shall be of the same force and effect as the provisions of 
this code 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 1 - General Requirement 1-3 



For the purpose of this code, certain terms, phrases, words 
and their derivatives shall be construed as specified in this 
chapter and elsewhere in this code where specific 
definitions are provided. Terms, phrases and words used in 
the singular include the plural and vice versa. Terms, 
phrases and words used in the masculine gender include the 
feminine and vice versa. 

The following terms are defined for use in this code: 

ALTER or ALTERATION is any change, addition or 
modification in construction or occupancy. 

APPROVAL shall mean that the proposed work or 
completed work conforms to this code in the opinion of the 
Building Official. 

APPROVED as to materials and types of construction, 
refers to approval by the Building Official as the result of 
investigation and tests conducted by the Building Official, 
or by reason of accepted principles or tests by recognized 
authorities, technical or scientific organizations. 

AS GRADED is the extent of surface conditions on 
completion of grading. 

AUTHORITY HAVING JURISDICTION is the 
organization, political subdivision, office or individual 
charged with the responsibility of administering and 
enforcing the provisions of this code. 

BEDROCK is in-place solid or altered rock. 

BENCH is a relatively level step excavated into earth 
material on which fill is to be placed. 

BORROW is earth material acquired from an off-site 
location for use in grading on a site. 

BUILDING is any structure usually enclosed by walls 
and a roof, constructed to provide support or shelter for an 
intended use or occupancy. 


BUILDING OFFICIAL is the officer or other designated 
authority charged with the administration and enforcement 
of this code, or the Building Official’s duly authorized 
representative. 

CIVIL ENGINEER is a professional engineer licensed to 
practice in the field of civil engineering. 

CIVIL ENGINEERING is the science or profession in 
which a knowledge of the mathematical and physical 
sciences gained by study and practice is applied with 
judgement to utilize natural and man-made resources and 
forces in the planning, design, management, construction, 
and maintenance of buildings, structures, facilities, and 
utilities in their totality, for the progressive well-being and 
for the benefit of mankind, enhancing the environment, 
community living, industry, and transportation, taking into 
consideration such aspects as functionality, efficiency, 
economy, safety, and environmental quality. 

COMPACTION is the densification of a fill by 
mechanical or chemical means. 

CONSTRUCTION FAILURE is a failure that occurs 
during construction and they are considered to be either a 
collapse or distress, of a structural system to such a degree 
that it cannot safely serve its intended purpose . 1 

CONTINUOUS STRUCTURAL INSPECTION is a 
structural inspection where the structural inspector is on the 
site at all times observing the work requiring structural 
inspection. 

EARTH MATERIAL is any rock, natural soil or fill or 
any combination thereof. 

ENGINEER-OF-RECORD is a civil engineer responsible 
for the structural design. 

EROSION is the wearing away of the ground surface as a 
result of the movement of wind or water. 

EXCAVATION is the mechanical removal of earth 
material. 

EXISTING GRADE is the grade prior to grading. 


BUILDING, EXISTING is a building erected prior to the FAILURE is defined as an unacceptable difference 

ac option of this code, oi one for which a legal between expected and observed performance. This 

building permit has been issued. definition includes catastrophic structural collapse, but also 

includes performance problems that are not necessarily 
catastrophic or life-threatening, including “serviceability 
problems such as distress, excessive deformation, 
premature deterioration of materials, leaking roofs and 
facades, and inadequate interior environmental control 
systems.” In the event of a significant failure, the parties 
typically retain experts to determine the cause of the 
perceived failure. Occasionally a failure results from a 
National Structural Code of the Philippines Volume 1, 7th Edition, 2015 


1-4 CHAPTER 1 - Genera! Requirements 


single condition, but typically, failures result from a 
combination of mistakes, oversights, miscommuni cations, 
misunderstandings, ignorance, lapses, slips, incompetence, 
intentional violations or non-compliance, and inadequate 
quality assurance. The causes for these conditions vary, but 
may include simple mistakes (such as sending information 
to a structural engineer when it should have been sent to the 
architect), conclusions based on faulty assumptions, an 
employee's “laziness, ignorance, or malevolent urge, 
fatigue from excessive workload, inadequate training, “time 
boxing'' practices used to minimize fees to a client, 
overreliance on computer-aided design and drafting 
(CADD), failure to understand and deliver client 
requirements, time pressures to a deliver a project by 
certain deadlines, and ineffective coordination and 
integration of the design team . 2 

FILL is a deposit of earth material placed by artificial 
means. 

FINISH GRADE is the final grade of the site that 
conforms to the approved plan. 

FORENSIC ENGINEERING is the application of the art 
and science of engineering in the jurisprudence system, 
requiring the services of legally qualified engineers. 
Forensic engineering may include investigation of the 
physical causes of accidents and other sources of claims 
and litigation, preparation of engineering reports, testimony 
at hearings and trials in administrative or judicial 
proceedings, and the rendition of advisory opinions to 
assist the resolution of disputes affecting life or property/ 

GENERAL COLLAPSE is the immediate, deliberate 
demolition of an entire structure by a triggering event (e.g, 
explosion)/ 7 

GEOTECHNICAL ENGINEER is a registered Civil 
Engineer with special qualification in the practice of 
Geotechnical Engineering as recognized by the Board of 
Civil Engineering of the Professional Regulation 
Commission as endorsed by the Specialty Division of 
Geotechnical Engineering of the Philippine Institute of 
Civil Engineers (PICE). 

GEOTECHNICAL ENGINEERING is the application of 
the principles of soil and rock mechanics in the 
investigation, evaluation and design of civil works 
involving the use of earth materials and foundations and the 
inspection or testing of the construction thereof 

GRADE is the vertical location of the ground surface. 

GRADING is an excavation or fill or combination thereof 

KEY is a designed compacted fill placed in a trench 
excavated in earth material beneath the toe of a slope. 


LIMITED LOCAL COLLAPSE is a failure of a 
structural member without affecting the adjacent members 
(e.g. destruction of one or two columns in a multi-bay 
structure)/ 

OCCUPANCY is the purpose for which a building or 
other structures or part thereof, is used or intended to be 
used. 

PERIODIC STRUCTURAL INSPECTION is a 
structural inspection where the inspections are made on a 
periodic basis and satisfy the requirements of continuous 
inspection, provided this periodic scheduled inspection is 
performed as outlined in the inspection program prepared 
by the structural engineer. 

PREFABRICATED ASSEMBLY is a structural unit, the 
integral parts of which have been built up or assembled 
prior to incorporation in the building. 

PROFESSIONAL INSPECTION is the inspection 
required by this code to be performed by the civil engineer. 
Such inspections include that performed by persons 
supervised by such engineer and shall be sufficient to form 
an opinion relating to the conduct of the work. 

PROGRESSIVE COLLAPSE is the spread of an initial 
local failure from element to element, eventually resulting 
in the collapse of an entire structure or disproportionately 
large part o f it . 4 

ROBUSTNESS is the insensibility of a structure to local 
failure. From this definition, it follows that the robustness 
is a property of the structure/ 

ROUGH GRADE is the stage at which the grade 
approximately conforms to the approved plan. 

SITE is any lot or parcel of land or contiguous combination 
thereof, under the same ownership, where grading is 
performed or permitted. 

SLOPE is an inclined ground surface the inclination of 
which is expressed as a ratio of vertical distance to 
horizontal distance. 

SOIL is naturally occurring superficial deposits overlying 
bedrock. 

SOILS ENGINEER See Geotechnical Engineer. 

SOILS ENGINEERING See Geotechnical Engineering, 

STRUCTURE is that which is built or constructed, an 
edifice or building of any kind, or any piece of work 
artificially built up or composed of parts joined together in 
some definite manner. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 1 - Genera! Requirement 1-5 


STRUCTURAL ENGINEER is a registered Civil 
Engineer with special qualification in the practice of 
Structural Engineering as recognized by the Board of Civil 
Engineering of the Professional Regulation Commission or 
by the Specialty Division of the Philippine Institute of Civil 
Engineers (PICE) together with the Association of 
Structural Engineers of the Philippines (ASEP) and 
Institution of Specialist Structural Engineers of the 
Philippines (ISSEP). 

STRUCTURAL ENGINEERING is a discipline of civil 
engineering dealing with the analysis and design of 
structures that support or resist loads insuring the safety of 
the structures against natural forces. 

STRUCTURAL FAILURE is the reduction of capability 
of a structural system or component to such a degree that it 
cannot safely serve its intended purpose. 5 

Structural failures can be divided into various categories 
based on consequential damages to include: Catastrophic 
Failure with Loss of Life, Catastrophic Failure in which No 
Human Lives are Endangered, Failure Resulting in 
Extensive Property Damage, and Failure Resulting in 
Reduced Serviceability. 5 

STRUCTURAL INSPECTION is the visual observation 
by a structural inspector of a particular type of construction 
work or operation for the purpose of ensuring its general 
compliance to the approved plans and specifications and 
the applicable workmanship provisions of this code as well 
as overall construction safety at various stages of 
construction. 

STRUCTURAL OBSERVATION is the visual 
observation of the structural system by the structural 
observer as provided for in Section 107.9.2, for its general 
conformance to the approved plans and specifications, at 
significant construction stages and at completion of the 
structural system. Structural observation does not include 
or waive the responsibility for the structural inspections 
required by Section 107. 1 or other sections of this code. 

TERRACE is a relatively level step constructed in the 
face of a graded slope surface for drainage and maintenance 
purposes. 

* Guide to Investigation of Structural Failures, ASCE, 1986. 

" The American Society of Civil Engineers (ASCE) Technical Council on 
Forensic Engineering. 

forensic Engineering,, T d Edition, KenethL Carper, Editor, 200 J. 

Robustness of Buildings in Structural Codes , Dimitris Diamantidis, 

2009 

Structu ral Failures in Buildings, ASCE, 1981. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


1-6 CHAPTER 1 - General Requirements 



.OF STRUCTURES 


103.1 Nature of Occupancy 

Buildings and other structures shall be classified, based on 
the nature of occupancy, according to Table 103-1 tor 
purposes of applying wind and earthquake loads in Chapter 
2. Each building or other structures shall be assigned to the 
highest applicable occupancy category or categories. 
Assignment of the same structure to multiple occupancy 
categories based on use and the type of loading condition 
being evaluated (e.g. wind or seismic) shall be permissible. 

When buildings or other structures have multiple uses 
(occupancies), the relationship between the uses of various 
parts of the building or other structure and the 
independence of the structural system for those various 
parts shall be examined. The classification for each 
independent structural system of a multiple-use building or 
other structure shall be that of the highest usage group in 
any part of the building or other structure that is dependent 
on that basic structural system. 


Table 103-1 Occupancy Category 


OCCUPANCY 

OCCUPANCY OR FUNCTION OF 


CATEGORY 

STRUCTURE 



Occupancies having surgery and emergency 



treatment areas. 

i 


Fire and police stations. 

} 


Garages and shelters for emergency vehicles and 



emergency aircraft, 



Structures and shelters in emergency preparedness 



centers. 

1 


Aviation control towers, 

. 


Structures and equipment in communication 

$ 


centers and other facilities required for emergency 

§ 

1 Essential 

response. 

'1 

Facilities 

Facilities for standby power-generating equipment 



for Category I structures. 

■; 


Tanks or other structures containing housing or 

\ 


supporting water or other fire-suppression material 

; 


or equipment required for the protection of 

j 


Category I, II or III, IV and V structres 



Public school buildings. 

1 


Hospitals, 

j 


Designated evacuation centers and 



Power and communication transmission lines. 



Occupancies and structures housing or supporting 

. 


toxic or explosive chemicals or substances, 


II Hazardous 


Facilities 

Non-building structures storing, supporting or 

■ 

containing quantities of toxic or explosive 



substances. 




Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 1 - General Requirement 1-7 


Table 103-1 (cont’d)Occupancy Category 


OCCUPANCY 

CATEGORY 

OCCUPANCY OR FUNCTION OF 
STRUCTURE 

III Special 

Occupancy 

Structures 

Buildings with an assembly room with an 
occupant capacity of l ,000 or more. 

Educational buildings such as museums, 
libraries, auditorium with a capacity of 300 or 
more occupants. 

Buildings used for college or adult education 
with a capacity of 500 or more occupants. 

Institutional buildings with 50 or more 
incapacitated patients, but not included in 
Category 1, 

Mental hospitals, sanitariums, jails, prisons 
and other buildings where personal liberties of 
inmates are similarly restrained. 

Churches, Mosques, and other Religion 
Facilities, 

All structures with an occupancy of 5,000 or 
more persons. 

Structures and equipment in power-generating 
stations, and other public utility facilities not 
included in Category I or Category II, and 
required for continued operation. 

IV Standard 
Occupancy 
Structures 

All structures housing occupancies or 
havingfunctionsnotlistedinCategory I, II 
orl I JandCategory ' V. 

V Miscellaneous 
Structures 

Privategarages,carports,shedsandfences 
over 1 .Smhigh. 



MUM 

DESIGN REQUIREMENTS 

104.1 Strength Requirement 

Buildings, towers and other vertical structures and ail 
portions thereof shall be designed and constructed to 
sustain, within the limitations specified in this code, all 
loads set forth in Chapter 2 and elsewhere in this code, 
combined in accordance with Section 203, 

Design shall be in accordance with Strength Design, Load 
and Resistance Factor Design and Allowable Strength 
Design methods, as permitted by the applicable material 
chapters. 

104.2 Serviceability Requirement 
104.2.1 General 

Structural systems and members thereof shall be designed 
to have adequate stiffness to limit deflections, lateral drifts, 
vibration, or any other deformations that adversely affect 
the intended use and performance of buildings, towers and 
other vertical structures. The design shall also consider 
durability, resistance to exposure to weather or aggressive 
environment, crack control, and other conditions that affect 
the intended use and performance of buildings, towers and 
other vertical structures. 

104.3 Analysis 

Any system or method of construction to be used shall be 
based on a rational analysis in accordance with well- 
established principles of mechanics that take into account 
equilibrium, general stability, geometric compatibility and 
both short-term and long-term material properties. 
Members that tend to accumulate residual deformations 
under repeated service loads shall have included in their 
analysis the added eccentricities expected to occur during 
their service life. Such analysis shall result in a system 
that provides a complete load path capable of transferring 
all loads and forces from their point of origin to the 
load- resisting elements. The analysis shall include, but not 
be limited to, the provisions of Sections 104.3.1 
through 104.3.3. 


104.3.1 Stability against Overturning 

Every structure shall be designed to resist the overturning 
effects caused by the lateral forces specified with adequate 
Factor of Safety (FOS). See Section 206.6 for retaining 
wails, Section 207 for wind loading and Section 208 for 
earthquake loading. 


National Structural Code of the Philippines Volume !, 7th Edition, 2015 



1-8 CHAPTER 1 - General Requirements 


104.3.2 Self-Straining Forces 

Provisions shall be made for anticipated self-straining 
forces arising from differential settlement of foundations 
and from restrained dimensional changes due to 
temperature, moisture, shrinkage, heave, creep and similar 
effects. 

104.3.3 Anchorage 

Anchorage of the roof to walls and columns, and of walls 
and columns to foundations shall be provided and 
adequately detailed to resist the uplift and sliding forces 
that result from the application of the prescribed forces. 

Concrete and masonry walls shall be anchored to all floors, 
roofs and other structural elements that provide lateral 
support for the wall. Such anchorage shall provide a 
positive direct connection capable of resisting the 
horizontal forces specified in Chapter 2 but not less than 
the minimum forces in Section 206.4. 

104.4 Foundation Investigation 

Soil explorations shall be required for buildings, towers and 
other vertical structures falling under Categories I, 11,11 1 
and IV in accordance with Table 103-1 or as required by 
the Building Official or If the site specific conditions 
make the foundation investigation necessary. 

Detailed requirements for foundation investigations shall be 
in accordance with Chapter 3 of this code. 

104.5 Design Review 

The design calculations, drawings, specifications and 
other design-related documents for buildings, towers and 
other vertical structures with irregular configuration in 
Occupancy Categories I, II or III within Seismic Zone 4, 
structures under Alternative Systems in Section 101.4, and 
Undefined Structural Systems not listed in Table 
208-11, shall be subject to a review by an independent 
recognized structural engineer or engineers to be employed 
by the owner in accordance with the ASEP Design Peer 
Review Guidelines. The structural engineer or structural 
engineers performing the review shall have comparable 
qualifications and experience as the structural engineer 
responsible for the design. The reviewer or reviewers shall 
obtain a professional waiver from the engineer-of-record 
who shall be expected to grant such waiver in keeping with 
ethical standards of the profession as adopted in ASEP 
guidelines for peer review (Appendix 1-A). 

The design review shall, as a minimum, verify the general 
compliance with this code which shall include, but not be 
limited to, the review of the design load criteria, the 
design concept, mathematical model and techniques. 


The following may also be verified, that there are no major 
errors in pertinent calculations, drawings and specifications 
and may also ensure that the structure as reviewed, meet 
minimum standards for safety, adequacy and acceptable 
standard design practice. 

The engineer-of-record shall submit the plans and 
specifications, a signed and sealed statement by the 
structural engineer doing the review that the above review 
has been performed and that minimum standards have been 
met. 

See Section 208.5,3.6.3.2 for design review requirements 
when nonlinear time-history analysis is used for earthquake 
design. 

In keeping with the ethical standards of the profession, the 
reviewer or reviewers shall not supplant the engineer-of- 
record as engineer-of-record for the project. The design 
review shall not in any way transfer or diminish the 
responsibility of the engineer-of-record. 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 1 - General Requirement 1-9 



105.1 Posting of Live Loads 


The live loads for which each floor or portion thereof of a 
commercial or industrial building has been designed shall 
have such design live loads conspicuously posted by the 
owner in that part of each story in which they apply, using 
durable metal signs. It shall not be allowed to remove or 
deface such notices. The occupant of the building shall be 
responsible for keeping the actual load below the allowable 
limits. 

1 05.2 Earthquake-Recording Instrumentation 

105.2.1 General 

Unless waived by the Building Official, every building in 
Seismic Zone 4 over 50 m in height shall be provided with 
not less than three approved Earthquake Recording 
Instalments (ERI). The ERI shall be interconnected for 
common start and common timing. Please refer to “ASEP 
Guidelines and Implementing Rules on Earthquake 
Recording Instrumentation for Buildings (Appendix 1-B). 

105.2.2 Location 

The instruments shall be located in the basement, 
midportion, and near the top of the building. Each 
instrument shall be located so that access is maintained at 
all times and is unobstructed by room contents. A sign 
stating “MAINTAIN CLEAR ACCESS TO THIS 
INSTRUMENT” shall be posted in a conspicuous 
location. 

105.2.3 Maintenance 

Maintenance and service of the instruments shall be 
provided by the owner of the building, subject to the 
monitoring of the Building Official. Data produced by the 
instruments shall be made available to the Building Official 
or any authorized agency upon request. 

105.2.4 Instrumentation of Selected Buildings 

All owners of existing structures selected by the 
authorities having jurisdiction shall provide accessible 
space for the installation of appropriate earthquake- 
recording instruments, determined by a Structural Engineer. 



(SECTIONS 
iSPECIFICATI* 
fcALCilATlONSlil 





106.1 General 


Copies of design calculations, reports, plans, 
specifications and inspection program for all 
constructions shall bear the signature and seal of the 
engineer-of-record. 

106.2 Specifications 

The specifications shall contain information covering the 
material and construction requirements. The materials and 
construction requirements shall conform to the 
specifications referred to in Chapters 1 to 7 of this code. 

106.3 Design Drawings 

106.3.1 General 

The design drawings shall be drawn to scale on durable 
paper or cloth using permanent ink and shall be of 
sufficient clarity to indicate the location, nature and extent 
of the work proposed.The drawings shall show a complete 
design with sizes, sections, relative locations and 
connection details of the various members. Floor levels, 
column centers and offsets shall be dimensioned. Where 
available and feasible, archive copies shall be maintained in 
durable medium such as compact disc (CD) and digital 
versatile disc (DVD). 

106.3.2 Required Information 

The design drawings shall contain, but shall not be limited 
to the general information listed in Section 106.3.2.1 and 
material specific information listed in Sections 106.3.2.2 
and 106.3.2.3, as applicable. 

106.3.2.1 General Information 

1. Name and date of issue of building code and 
supplements, if any, to which the design conforms. 

2. Strengths or designations of materials to be used. 

3. Design strengths of underlying soil or rock. The soil 
or rock profile, when available, shall be provided. 

4. Live loads and other loads used in design and clearly 
indicated in the floor plans. 


National Structural Code of the Philippines Volume i, 7th Edition, 2015 


1-10 CHAPTER 1 - General Requirements 


5. Seismic design basis including the total base shear 
coefficient; a description of the lateral load resisting 
system; and the fundamental natural period in the 
design in each direction under consideration. 

6. Provisions for dimensionatchanges resulting from 
creep, shrinkage, heave and temperature. 



TESTS AND STRUCTURAL 


107.1 General 


7. Camber of trusses, beams and girders, if required. 

8. Explanation or definition of symbols and 
abbreviations used in the drawings. 

9. Engineer-of-Record’s professional license number 
and expiration date of the current Professional 
Regulation Commission registration (PRC), 


All construction or work for which a permit is required 
shall be subject to inspection throughout the various work 
stages. One or more structural inspectors who are registered 
civil engineers with experience in structural construction, 
who shall undertake competent inspection during 
construction on the types of work listed under Section 
107.5, shall be employed by the owner or the engineer-of- 
record acting as the owner's agent. 


106.3.2.2 Structural Concrete 

1. Specified compressive strength (f' c ) of concrete at 
stated ages or stages of construction for which eachpart 
of structure designed. The 28-day compressive strength 
(f' c ) shall be the basis of design in service condition. 

2. Anchorage embedment lengths or cut-off points of 
steel reinforcement and location and length of lap 
splices. 

3. Type and location of welded splices and mechanical 
connections of reinforcement. 

4. Magnitude and location of prestressing forces 
including prestressed cable layout 

5. Minimum concrete compressive strength (/ a *')at time 
of post-tensioning. 

6. Stressing sequence for post-tensioned tendons. 

7. Details and location of all contraction or isolation 
joints specified for plain concrete in Chapter 4. 

8. Statement if concrete slab is designed as a structural 
diaphragm, as specified in Sections 421.9.4 and 
421.9.5. 


Exception: 

The Building Official may waive the requirement for the 
employment of a structural inspector if the construction is 
of a minor nature . 

In addition to structural inspections, structural observations 
shall be performed when required by Section 107.9. 

107.2 Definitions 

See Section 102 for definitions. 

107.3 Structural Inspector 

1 07.3.1 Qualifications 

The structural inspector shall be a registered civil engineer 
who shall demonstrate competence for inspection of the 
particular type of construction or operation requiring 
structural inspection. 

107.3.2 Duties and Responsibilities 

The structural inspector shall observe the work assigned for 
conformance to the approved design drawings and 
specifications. Any discrepancy observed shall be brought 
to the immediate attention of the constructor for correction, 
then, if uncorrected, to the owner, engineer-of-record 
and/or to the Building Official. 


The structural inspector shall verify that the as-built 
drawings (see Section 106.5) pertaining to the work 
assigned reflect the condition as constructed. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 1 - General Requirement 1-11 


The structural inspector shall also submit a final report duly 
signed and sealed stating whether the work requiring 
structural inspection was, to the best of the inspector's 
knowledge, in conformance to the approved plans and 
specifications and the applicable workmanship provisions 
of this code. 

107.4 Inspection Program 

The structural inspector shall prepare an appropriate testing 
and inspection program that shall be submitted to the 
owner, engineer-of-record and/or to the Building Official. 
He shall designate the portions of the work that requires 
structural inspections. 

When structural observation is required by Section 107.9, 
the inspection program shall describe the stages of 
construction at which structural observation is to occur. 

The inspection program shall include samples of inspection 
reports and provide time limits for submission of reports. 

107.5 Types of Work for Inspection 

Except as provided in Section 107.1, the types of work 
listed below shall be inspected by a structural inspector. 

107.5.1 Concrete 

During the taking of test specimens and placing of 
concrete. See Section 107.5.12 for shotcrete. 

Exceptions: 

L Concrete for foundations of residential buildings 
accommodating 10 or fewer persons , or buildings 
falling under Category K of Table 103-1, provided the 
Building Official finds that a structural hazard does 
not exist, 

2. For foundation concrete, other than cast-in-place 
drilled piles or caissons , where the s tructural design is 
based on anf l c not greater than 1 7 MPa . 

3. Non-striictiiral slabs on grade , including pres tressed 
slabs on grade when effective prestress in concrete is 
less than 10 MPa, 

4 . Site work concrete fully supported on earth and 
concrete where no special hazard exists. 

107.5.2 Bolts Installed in Concrete 

Prior to and during the placement of concrete around bolts 
when stress increases permitted by Section 426 are utilized. 


107.5.3 Special Moment-Resisting Concrete Frame 

For special moment-resisting concrete frame design seismic 
load in structures within Seismic Zone 4, the structural 
inspector shall provide reports to the engineer-of-record 
and shall provide continuous inspection of the placement of 
the reinforcement and concrete. 

107.5.4 Reinforcing Steel and Prestrcssing Steel 
Tendons 

107.5.4.1 During all stressing and grouting of tendons in 
prestressed concrete. 

107.5.4.2 During placing of reinforcing steel and 
prestressing tendons for all concrete required to 
have structural inspection by Section 107.5.1, 

Exception: 

The structural inspector need not be present continuously 
during placing of reinforcing steel and prestressing 
tendons, provided the structural inspector has inspected for 
conformance to the approved plans prior to the closing of 
forms or the delivery of concrete to the jobsite . 

107.5.5 Structural Welding 
107.5.5.1 General 

During the welding of any member or connection that is 
designed to resist loads and forces required by this code. 

Exceptions: 

L Welding done in an approved fabricator's shop in 
accordance with Section 107.6. 

2. The structural inspector need not he continuously 
present during welding of the following items, 
provided the materials, qualifications of welding 
procedures and welders are verified prior to the start 
of work; periodic inspections are made of work in 
progress; and a visual inspection of all welds is made 
prior td completion or prior to shipment of shop 
.... welding: 

a)Single-pass fillet welds not exceeding H mm in size. 

b) Floor and roof deck welding. 

c) Welded studs when used for structural diaphragm 
or composite systems.. 

d) Welded sheet steel for cold-formed steel framing 
members such as studs and joists. 

e) Welding of stairs find railing systems. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


1-12 


CHAPTER 1 - General Requirements 


107.5.5.2 Special Moment-Resisting Steel Frames 

During the non-destructive testing (NDT) of welds 
specified in Section 107.8 of this code, the use of certified 
welders shall be required for welding structural stee 
connections for this type of frame. Critical joint 
connections shall be subjected to non-destructive testing 
using certified NDT technicians. 

107.5.5.3 Welding of Reinforcing Steel 
During the non-destructive testing of welds. 


107.5.6 High-Strength Bolts 

The inspection of high-strength A325 and A490 bolts shall 
be in accordance with approved internationally recognizee 
standards and the requirements of this section. While the 
work is in progress, the structural inspector shall determine 
that the requirements for bolts, nuts, washers and paint, 
bolted parts; and installation and tightening in such 
standards are met. Such inspections may be performed on 
a periodic basis as defined in Section 107. 

The structural inspector shall observe the calibration 
procedures when such procedures are required by the plans 
or specifications. He shall monitor the installation of bolts 
to determine that all layers of connected materials have 
been drawn together and that the selected procedure is 
properly used to tighten alt bolts. 


107.5.7 Structural Masonry 

107.5.7.1 For masonry, other than fully grouted open-end 
hollow-unit masonry, during preparation and taking of any 
required prisms or test specimens, placing of all masonry 
units, placement of reinforcement, inspection of grout 
space, immediately prior to closing of cleanouts, and during 
all grouting operations. 


Exception: 

For hollow-unit masonry where thef,„ is no more than 10 
MPa for concrete units or IS MPa for clay units, structural 
inspection may be performed as required for fully grouted 
open-end hollow-unit masonry specified m Section 
107:5:7.2. 


107 5 7,2 For fully grouted open-end hollow-unit masonry 
during preparation and taking of any required prisms or test 
specimens, at the start of laying units, after the placement 
of reinforcing steel, grout space prior to each grouting 
operation, and during all grouting operations. 

Exception: 

Structural inspection as required in Sections 107.5.7.1 and 
107 5 7 2 need not be provided when design stresses have 
been ' adjusted as specified in Chapter 7 to permit 
noncontinuous inspection. 

107.5.8 Reinforced Gypsum Concrete 

When cast-in-place Class B gypsum concrete is being 
mixed and placed. 

107.5.9 Insulating Concrete Fill 

During the application of insulating concrete till when used 
as part of a structural system. 

Exception: 

The structural inspections may be limited to an initial 
inspection to check the deck surface and placement of 
reinforcing steel. The structural inspector shall monitor tlm 
preparation of compression test specimens during this 
initial inspection 


107.5.10 Spray-Applied Fire-Resistive Materials 

During the application of spray-applied fire-resistive 
materials. 

107.5.11 Piling, Drilled Piers and Caissons 

During driving and load testing of piles and construction of 
cast-in-place drilled piles or caissons. See Sections 107.5.1 
and 107.5.4 for concrete and reinforcing steel inspection. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 1 - General Requirement 1-13 


107.5.12 Shotcrete 

During the taking of test specimens and placing of all 
shotcrete. 

| ^cepti<m:fev, 

Shotcrete work fully supported on earth, minor repairs and 
when, in the opinion of the Building Official, no special 

hazard exists. 

107.5.13 Special Grading, Excavation and Filling 

During earthwork excavations, grading and filling 
operations inspection to satisfy requirements of Chapter 3 
and Section 109.5. 

107.5.14 Special Cases 

Work that, in the opinion of the structural engineer, 
involves unusual hazards or conditions. 

107.5.15 Non-Destructive Testing 

In-situ non-destructive testing program, in addition to the 
requirements of Section 107.8 that in the opinion of the 
structural engineer may supplement or replace conventional 
tests on concrete or other materials and assemblies. 

107.6 Approved Fabricators 

Structural inspections required by this section and 
elsewhere in this code are not required where the work is 
done on the premises of a fabricator approved by the 
structural engineer to perform such work without structural 
inspection. The approved fabricator shall submit a 
certificate of compliance that the work was performed in 
accordance with the approved plans and specifications to 
the Building Official and to the engineer or architect-of- 
record. The approved fabricator’s qualifications shall be 
contingent on compliance with the following: 

1. The fabricator has developed and submitted a detailed 
fabrication procedural manual reflecting key quality 
control procedures that will provide a basis for 
inspection control of workmanship and the fabricator 
plant. 


2. Verification of the fabricator’s quality control 
capabilities, plant and personnel as outlined in the 
fabrication procedural manual shall be by an approved 
inspection or quality control agency. 

3. Periodic plant inspections shall be conducted by an 
approved inspection or quality control agency to 
monitor the effectiveness of the quality control 
program. 

107.7 Prefabricated Construction 

107.7.1 General 

107.7.1.1 Purpose 

The purpose of this section is to regulate materials and 
establish methods of safe construction where any structure 
or portion thereof is wholly or partially prefabricated, 

107.7.1.2 Scope 

Unless otherwise specifically stated in this section, all 
prefabricated construction and all materials used therein 
shall conform to all the requirements of this code. 

107.7.1.3 Definition 

See Section 102 for Definitions. 

107.7.2 Tests of Materials 

Every approval of a material not specifically mentioned in 
this code shall incorporate as a proviso the kind and 
number of tests to be made during prefabrication. 

107.7.3 Tests of Assemblies 

The Building Official may require special tests to be made 
on assemblies to determine their structural adequacy, 
durability and weather resistance. 

107.7.4 Connections 

Every device used to connect prefabricated assemblies shall 
be designed as required by this code and shall be capable of 
developing the strength of the largest member connected, 
except in the case of members forming part of a structural 
frame designed as specified in Chapter 2. Connections 
shall be capable of withstanding uplift forces as speci fied in 
Chapter 2. 

107.7.5 Pipes and Conduits 

In structural design, due allowance shall be made for any 
material to be removed or displaced for the installation of 
pipes, conduits or other equipment. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


1-14 CHAPTER 1 - Genera! Requirements 


107.7.6 Certificate and Inspection 

107.7.6.1 Materials 

Materials and the assembly thereof shall be inspected to 
determine compliance with this code. Every material shall 
be graded, marked or labeled where required elsewhere in 
this code. 

107.7.6.2 Certificate 

A certificate of acceptance shall be furnished with every 
prefabricated assembly, except where the assembly is 
readily accessible to inspection at the site. The certificate 
of acceptance shall certify that the assembly in question has 
been inspected and meets ail the requirements of this code. 

107.7.6.3 Certifying Agency 

To be acceptable under this code, every certificate of 
approval shall be made by a nationally or internationally 
recognized certifying body or agency, 

107.7.6.4 Field Erection 

Placement of prefabricated assemblies at the building site 
shall be inspected to determine compliance with this code. 

107.7.6.5 Continuous Inspection 

If continuous inspection is required for certain materials 
where construction takes place on the site, it shall also be 
required where the same materials are used in prefabricated 
construction. 

Exception: 

Continuous inspection will not be required during 
prefabrication if the approved agency certifies to the 
construction and furnishes evidence of compliance. 

107.8 Non-Destructive Testing 

107.8.1 General 

In Seismic Zone 4, welded, fully-restrained connections 
between the primary members of special moment-resisting 
frames shall be tested by nondestructive methods 
performed by certified NDT technicians for compliance 
with approved standards and job specifications. This testing 
shall be a part of the structural inspection requirements of 
Section 107.5. A program for this testing shall be 
established by the person responsible for structural design 
and as shown on plans and specifications. 


107.8.2 Testing Program 

As a minimum, the testing program shall include the 
following: 

107.8.2.1 All complete penetration groove welds 
contained in joints and splices shall be tested 
100 percent either by ultrasonic testing or by 
radiography. 

Exceptions : 

L When approved , the non-destructive testing rate for an 
individual welder or welding operator may be reduced 
to 25 percent , provided the reject rate is demonstrated 
to be 5 percent or less of the welds tested for the 
welder or welding operator. A sampling of at least 40 
completed welds for a job shall be made for such 
reduction evaluation. Reject rate is defined as the 
number of welds containing rejectable defects divided 
by the number of welds completed \ For evaluating the 
reject rate of continuous welds over 900 mm in length 
where the effective throat thickness is 25 mm or less , 
each 300 mm increment or fraction thereof shall be 
considered as one weld. For evaluating the reject rate 
on continuous welds over 900 mm in length where the 
effective throat thickness is greater than 25 mm, each 
150 mm of length or fraction thereof shall he 
considered one weld. 

2. For complete penetration groove welds on materials 
less than S mm thick non-destructive testing is not 
required; for this welding, continuous inspection is 
required. 

3. When approved by the Building Official and outlined 
in the project plans and specifications, this non- 
destructive ultrasonic testing mew he performed in the 
shop of an approved fabricator utilizing qualified test 
techniques in the employment of the fabricator. 

107.8.2.2 Partial penetration groove welds when used in 
column splices shall be tested either by ultrasonic testing or 
radiography when required by the plans and specifications. 
For partial penetration groove welds when used in column 
splices, with an effective throat less than 20 mm thick, 
nondestructive testing is not required; for this welding, 
continuous structural inspection is required. 

107.8.2.3 Base metal thicker than 40 mm, when subjected 
to through-thickness weld shrinkage strains, shall be 
ultrasonicaily inspected for discontinuities directly behind 
such welds after joint completion. 

Any material discontinuities shall be accepted or rejected 
on the basis of the defect rating in accordance with the 
(larger reflector) criteria of approved national standards. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


107.8.3 Others 

The structural engineer may accept or require in place non- 
destructive testing of concrete or other materials and 
assemblies to supplement or replace conventional tests. 

107.9 Structural Observation 

107.9.1 General 

Structural observation shall be provided in Seismic Zone 4 
when one of the following conditions exists: 

1. The structure is defined in Table 103-1 as Occupancy 
Category I, II , III and IV.; 

2. The structure is in Seismic Zone 4, N a as set forth in 
Table 208-4 is greater than 1.0, and a lateral design is 
required for the entire structure; 

3. When so designated by the structural engineer, or 

4. When such observation is specifically required by the 
Building Official. 

107.9.2 Structural Observer 

The owner shall employ the engineer-of-record or another 
civil engineer to perform structural observation as defined 
in Section 107. 

Observed deficiencies shall be reported in writing to the 
owner's representative, structural inspector, constructor and 
the Building Official. If not resolved, the structural 
observer shall submit to the Building Official a written 
statement duly signed and sealed, identifying any 
deficiency. 

107.9.3 Construction Stages for Observations 

The structural observations shall be performed at the 
construction stages prescribed by the inspection program 
prepared as required by Section 107.4, 

It shall be the duty of the engineer-in-charge of 
construction, as authorized in the Building Permit, to notify 
the structural observer that the described construction 
stages have been reached, and to provide access to and 
means for observing the components of the structural 
system. 


CHAPTER 1 - General Requirement 1-15 


National Structural Code of the Philippines Volume l, 7th Edition, 2015 



National Structural Code of the Philippines Volume I, 7th Edition, 2015 





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About this Guidelines 

Recommended Guidelines on Structural Design Peer Review of Structures 2015 
Published by Association of Structural Engineers of the Philippines, Inc. 


Copyright© 2015 

Association of Structural Engineers of the Philippines, Inc. (ASEP) 
Suite 713 Future Point Plaza Condominium 1, 

1 12 Panay Avenue, Quezon City, 

1100 Philippines 


Telephone Nos. 
Facsimile 
E-mail Address 
Website 


+63 (2)410-0483 
+63 (2)411-8606 
aseponline@gmail.com 
http://www.aseponline.org 


About ASEP 

The Association of Structural Engineers of the Philippines, Inc. (ASEP) is the recognized organization of Structural 
Engineers of the Philippines. Established in 1961, ASEP has been in existence for more than 50 solid years. 



Print History 
2000 
2015 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


IA-5 


CONTENTS 


ABBREVIATIONS 

INTRODUCTION 

BACKGROUND 

OBJECTIVES OF THE DESIGN PEER REVIEW 

APPLICATION OF ASEP PEER REVIEW GUIDELINES j_ A9 

EXPECTED RESULTS OF DESIGN REVIEW: 

STRUCTURES TO BE REVIEWED 

REVIEWER’S QUALIFICATION 

SCOPE OF REVIEW 

INFORMATION TO BE FURNISHED TO PEER REVIEWER j_ A11 

ITEMS TO BE REVIEWED n 

METHODOLOGY AND DETAILS OF REVIEW 

Design Basis Review j _ ^ j j 

Foundation Review j ^ 

Pre-Tender Design Review 1-A16 

MINIMUM REPORT REQUIREMENTS 

Content I-A16 

Terms of Review Procedure and Methodology to he Used 1-A17 

Language to be Used I-A17 

Mark-up and Comments I-A17 

Examples of Revie wer 's Comments/Wordings j g 

REFERENCES 


Recommended Guidelines on Structural Design 
Peer Review of Structures 2015 


1A-6 


Abbreviations 


A&D 


ACI 


AISC 


ASCE 


ASEP 


BIM 


CE 


CTBUH 


DPWH 


Analysis and Design 


American Concrete Institute 


American Institute of Steel Construction 


American Society of Civil Engineers 


Assoc iation of Structural Engineers of the Philippines, Inc. 


Building Information Model 


Civil Engineer 


Council on Tall Buildings and Urban Habitat 


Department of Public Works and Highways_ 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 


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Introduction 


Design review is incorporated in most building codes to provide the means for professional discussion and evaluation of 
structural design ot projects. Thus, these reviews are the eye openers for the resolution of problems encountered before a critical 
phase of the construction project. Design review truly enhances the ideas for public safety overall and quality assurance. 
Furthermore, it disseminates innovation through sharing of information. 

Earthquake for instance is a phenomenon that man has been trying to study for centuries but up to present time is still 
unpredictable. We, as structural engineers, are faced with the greatest challenge of formulating procedures on how to lessen if 
not eliminate destruction and casualties due to this. We want to make sure that the intent of our design is carefully followed 
and carried out in the most professional manner. The burden o f setting up and observing rules on how to achieve what has been 
planned rest upon our shoulders. Design review can be a valuable tool faced with this challenge. 

This document establishes the guidelines for peer review. Since protecting lives and properties are the paramount goals of the 
Association of Structural Engineers of the Philippines (ASEP), the only way perhaps to realise these goals is to establish ground 
rules for all our practicing civil engineers, structural engineers and consultants to follow strictly the Code provisions and 
standards parameters. 

It is essential to good engineering practice to conduct independent peer review to achieve a concept of structural system and 
design tolerant to the crudeness in seismological predictions. The independent review of structures shall be deemed as the 
means to promote life safety, achieve excellence in structural design and front of quality, improvement/advancement and 
dissemination of structural engineering knowledge in the country. 


Recommended Guidelines on Structural Design 
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Background _ 

To accomplish the objectives of ASEP, the Board of Directors for 1 999-2000 has continued the program of the ASEP Board 
of Directors for 1998-1999 by creating several committees as shown below. These objectives, as stated in its by-laws, shall be 
the protection of the public welfare and the welfare of its constituents through the: 

e Maintenance of highly ethical and professional standards in the practice of engineering 

e Advancement of structural engineering knowledge; 

o Promotion of good public and private clientele relationships, development of fellowships among CE and SE and 
encouragement of professional relations with other allied technical and scientific organizations. 

These objectives are focused on these three major areas: 

o Codes and Standards 

o Fellowships and Linkages 

o Technical Advancement 

One of the committees created for the Codes and Standards is the Committee on Design Peer Review. The National Structural 
Code of the Philippines (NSCP) 1992 Edition touches on independent design review under the section “A Design and 
Construction Review", which defines the structures required for the review considering seismic zones and occupancy 
categories. However, the scope, procedures and documentation of the review process are not mentioned. Thus, this paper will 
include guidelines on the implementation of the design peer review. 

The same committee was revived by the President of the Board of Directors tor 2009-2010, Adam C. Abinales, from the point 
of view of engineering practitioners, to improve and expand the guidelines to incorporate additional parameters and ethical 
rules as well as enhance the practice of peer review. The committee's acti vities have continued under the administiation of the 
following ASEP Presidents: 

© Anthony Vladimir Pimentel (2010-201 1) 

© Vinci Nicholas R. Villasenor (201 1-2012) 

© Miriam L. Tamayo (2013) 

© Carlos M. Villaraza (2015) 

The Committee on Design Peer Review is composed of the following: 

Chairman 
Ernesto F. Cruz 

Co-Chairman 
Gabriel Ursus L, Eusebio 

Members 
Alden C. Ong 
Marie Christine G. Danao 
Edmondo D. San Jose 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


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Objectives of the Design Peer Review 


The current trend in the local construction industry is the development of many high-rise buildings* On account of this, it is the 
objective of this peer review to improve section 104*5 of NSCP 2010, to ensure the aim for life safety, to observe economy in 
design and to protect the investment of clients. 

The Peer Review aims to carry out positive results in the following areas: 

© to comply structural engineering design, drawings and specification with the minimum requirements of NSCP and other 
acceptable established codes and standards; 

© To maintain the quality of projects; 

© To improve and maintain the high standards in the practice of structural engineering; 

© To promote exchange of information and innovative ideas between the designers and reviewers; 

© To inform the Owner-Client on the benefits of this exercise and any possible cost implications resulting from the review; 
© To define implementing matrix of all structures subject to practical independent review; and 

© To promote professional ethics in the conduct of independent or peer review. 


Application of ASEP Peer Review Guidelines 


These ASEP guidelines are intended specifically for the mandatory conduct of a Design Review as per the National Structural 
Code of the Philippines (NSCP Volume 1, 2010 Edition). 

As stipulated in NSCP Section 104.5, Design Review is required for the following: 

1. Structures with irregular configuration in Occupancy Categories I (Essential Facilities), II (Hazardous Facilities) or III 
(Special Occupancy Structures) in Zone 4; 

2. Structures under Alternative Systems in Section 101 .4; and, 

3. Undefined Structural Systems (those not listed in Table 208-1 1). 

For structures covered by the mandatory Design Review, all related works shall be deemed as included in the Engineer-of 
Record’s scope of works, unless explicitly excluded in his work agreement. 

For structures not included above but which are to be subjected to a Design Review as an additional requirement by the Owner, 
the coverage, extent, and procedures shall be as mutually agreed upon by the Owner/Peer Reviewer, and the Engineer-of- 
Record (EOR) and may not be as recommended in these Guidelines. Additionally, since works connected or related to such 
Design Review are not covered by the basic structural services of the EOR, these shall be subject to a separate scope and 
compensation for the EOR. 


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Peer Review of Structures 201 5 


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Expected Results of Design Review: _ 

o As professionals, independent design reviewers and EOR shall not engage in unfair practices. Both shall 
observe fairness and professionalism in the practice of independent review. This shall not by any means be a 
channel to conduct criticism nor be a means to discredit the reviewer or the EOR, and disenfranchise them of 
the contract service they are awarded. 

, There will be good understanding of the structures and relationships between the Owner-Client and the 
structural engineering community resulting to enhanced programs of future developments and projects. 

• There will be good relationships between designers and reviewers by improving the design through constructive 
reporting. 

, The review will be conducted smoothly in the light of fairness and professionalism, without unfair practice and 
criticism to neither discredit nor disenfranchise any of the reviewer or EOR. 

® The review will bring assurance to the Owner-Client of compliance to codes and standards, assurance of bettei 
engineering of the proposed structure, the improvement in design and safety as well as improvement in 
construction implementation and program, elimination of unsafe design and possible work delays fiom 
unwanted and costly repairs, among others. 


Structures to be Reviewed — 

Structures to be reviewed shall consist of all proposed new structures and addition to structures which shall be deemed crucial 

to life safety and/or health of the public and peace if such structures or buildings would incur damage or failure or both. 

The structures to be reviewed shall be as follows: 

1 . All structures more than 75-meter high (whichever is higher) from the exterior ground level. 

2 Buildings towers and other vertical structures with irregularity in configuration (vertical and horizontal irregularity) undei 
occupancy Category I, II, and III (as per section 1 03.1 NSCP VI edition) within the seismic zone 4. 

3. Structures designed under alternative system (as per section 101.4 NSCP VI Edition) that intends to use other structural 
materials, design approach and construction methodology not prescribed by the latest; existing structural Code ( S 
Edition, 20 1 0) or by other recognized international codes and standards. 

4. Buildings, towers and other structures with undefined structural system not listed in Table 208-11 of NSCP VI Edition. 

5. Essential facilities such as hospitals fire & police stations, emergency vehicle and equipment shelters and garages, 
structures and equipment in communication center, aviation control towers, private and public school buildings, water 
supported structures and designated evacuation center, also buildings and structures for national defense. 

6 Hazardous Facilities and the like structures housing, supporting or containing sufficient quantities of toxic or explosive 
substances dangerous to the safety of the general public if released due to damage or excessive deformation. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


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Reviewer’s Qualification 


The independent PR shall be nominated by the Owner-Client. The independent PR shall not be the design EOR or engineer 
appointed by Builder/Contractor. In the case of Turnkey or Design and Build projects whose design is initiated by the 
Contractor or Developer, the Contractor at his own expense shall appoint an independent recognized structural engineer to 
conduct the services of design peer review. 

The independent PR shall have the following qualifications: 

1. Civil engineer registered with the Professional Regulation Commission of the Philippines with more than 20 years of 
related structural engineering experience similar to the structure to be reviewed. 

2. He must be a REGULAR ASEP Member in good standing. 

3. Structural Engineers with comparable qualification and experience as the EOR responsible for the design (as per latest 
NSCP). 

4. Knowledgeable in current design software, tools, and other acceptable current computer programs. 

5. Have competitive knowledge or experience in actual structural construction. 


Scope of Review 


The PR must review all items agreed to be reviewed with the Owner-Client and EOR per relevant/recommended items listed 
in this Guide. The PR shall refer regularly to check for completeness of the review per applicable items listed in these guidelines. 
The quantity of elements to be reviewed shall be in accordance with the second paragraph of the subsection Methodology of 
Review below. 


Information to be Furnished to Peer Reviewer 


The review documents should be checked for completeness and timeliness of the design documents submitted per relevant 

items recommended in this guide. The PR should assess the review documents received and report immediately to the Owner- 

Client and/or his duly appointed representative for the following: 

° If any of the design documents submitted are not sufficient for him to proceed with the review such that an entire document 
is missing, for example the design criteria document is not included and the drawings do not reflect the design 
parameters/information completely; or 

9 documents given and received may enable him to start and work immediately but the PR have to stop soon for some 

items of works as some documents are given as partial only; or 

® The documents given and submitted are irrelevant to the project; or 

° The documents received are of poor quality such as illegible, faintly printed, blurred, torn, and or unacceptably dirty or 
laced with hazardous materials. 


Recommended Guidelines on Structural Design 
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© The PR shall also report if the items received were not delivered in good condition that may not enable him to pioceed at 
all; e.g. the documents are wet due to improper handling, incomplete or inadequate protection from packaging materials, 
among others. 


The following items are to be furnished by the Owner-Client as applicable: 

□ Printed copies or PDF/DWFx format of complete set of architectural and structural drawings; 

D General building narrative (number of stories, gross building area, estimated construction cost, unique features, among 

others); 

□ Geotechnical engineering report; 

Q Wind Tunnel Test report (if any); 

□ Site-specific spectra and ground-motion time histories (if any); 

Q Major equipment or special loadings; 

□ Existing building drawings/data if impacted by or impacting the threshold structure; 

□ Analysis models including User’s Guide of software used by EOR (e.g. STAAD, ETABS, SAP, SAFE and midasGen). 
It is recommended to include also interoperable files such as .SET, .ANL, .S2K and .F2K to facilitate conversion of 
data.; 

Q 3D model/BIM 1 file or *.ifc 2 file (if any); 

□ Design basis; 

□ Design criteria; 

□ Structural systems design narrative (including wind and seismic design parameters); 

□ Structural elements design calculations; and 

□ Structural specifications. 


Items to be Reviewed _____ 

The PR may include as appropriate/appiicable any or all of the following: 


Table 1: Checklist of Items to be Reviewed 


Item 

Specific Design Checks to be Carried Out 

Design 

Basis/Criteria 

Minimum loadings as set out in the code. 

Prevailing site conditions and assumptions in design analysis. 

Materials used in the design and specifications. 


Reference to any assumed loadings, construction methods, A&D. 


Description of the operational language and/or algorithms, capability and source of the software used, 
including the proof of good comparison with results of known and accepted method of analysis. 


Seismic design parameters and base shear. _ — - 


Number of mass participation for dynamic analysis. 


1 Building Information Model (BIM) is a digital representation of physical and functional characteristics of a structure. As such it serves as 
a shared knowledge resource for information about a structure forming a reliable basis for decisions during its life cycle from inception 
onward. 

2 Industry Foundation Classes (.ifc) - A file format developed by the IAI. 1FC provides an interoperability solution between IFC-compatible 
software applications in the construction and facilities management industry. The format has established, international standards to import 
and export building objects and their properties. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



Item 

Specific Design Checks to be Carried Out 


Wind loadings design parameters and comfort criteria. 

Design 

Methods, 
Standards and 
Specifications 

Appropriateness to the Client’s technical brief and functional requirements. 

Conformance to the governing codes used in the analysis and design. 

Analysis 

models 

Input and output data including geometry, material constants, properties, loadings, assignments and 
parameters used in software used. 

Foundation 

|Loads 

Appropriate values of dead, live, wind and seismic loads used. 

Column loads have been appropriately computed and compared to results of analysis model. 

Effects of wind and notional loads on the building or structure have been checked. 

Piles 

Pile capacities have been designed for compressive axial load by applicable skin friction and end bearing 
capacities. 

Review if the type of pile reactions used in the analysis models are appropriate/applicable. 

Piles were checked if required/applicable for combined buckling. 

Piles have been designed for lateral loads and bending moment. 

Pile joints have been designed for anchorage and embedment length of reinforcements, for concrete pile. 

Piles have been designed for uplift. 

Socketing has been designed for piles with short penetration depths. 

Piles have been designed for negative skin friction. 

Isolated Pads/ 

Combined 

Footings/ 

Tied Footings 

Checked for punching shear and bending moments. 

Raft 

Appropriate allowable bearing capacity of soil has been assumed in design. 

Appropriate modulus of sub-grade reaction of the soil has been assumed in design. 

Appropriate model used for structural analysis of the raft. 

The raft has been designed to resist punching shear from columns. 

The building or structure has been designed to cater for probable differential and total settlement. 

Lateral Load 

Resisting 

Framing 

Systems as 
assumed in the 
Design Basis/ 
Criteria 

The presence in the structural framing of any plan and/or vertical irregularities mentioned in NSCP or 
governing codes. 

Limitations of lateral load resisting framing systems by NSCP, or by the Owner-Client preferred code and 
standards and or from any prevailing local ordinance and regulations in the vicinity of the proposed structure. 

Details of seismic-resistant concrete structure were checked. 

Slender 

Columns 

Effective height has been computed according to code. 

Bending moment about minor axis has been designed for. 

Additional bending moment due to slenderness has been designed for. 

Biaxial bending moment has been designed for. 

Requirement for ductility such as strong-column weak beam is provided or complies with the code. 

Columns 
supporting 
transfer beams 

Designed for bending moment due to frame action including effects of special load combination per code. 


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Item 

Specific Design Checks to be Carried Out 

Columns 
supporting long 

cmn herttriS 

Designed for bending moment due to frame action. 

Columns 

supporting 

cantilever 

Designed for bending moment due to frame action. 

Uvuli lo 

f’nliimnQ in fl 

Designed for horizontal load and moment acting on columns due to arched or pitched tool. 

v^uiuinuo in u _ 

two column 

Designed for bending moment and shear at the column base including connections. 

frame system 

Designed for bending moment due to frame action. 

Cantilever 

Cantilever support has been designed to resist bending moment and shear including minimum uplift loads 
from wind and seismic loads. — - — 


Designed for lateral stability of beam. - 

Designed to meet allowable span depth ratio; else deflection against allowable limit per code including long- 
term effects. 

Long span 
beams 

Torsional rigidity of beam has been checked. _ 

Designed for lateral restraint of beams. 

Designed for support and member connections. 

Designed to meet allowable span depth ratio; else deflection against allowable limit pei code including long- 
term effects. * — — 

Transfer beams 

Designed for torsional capacity. 

Designed for shear capacity. 

Designed for all relevant upper floor loads on the beam including effects of special load combinations pet 
code. — — 

Designed for lateral restraint of beam. 

Flat slabs/plates 

Appropriate model used for analysis. __ — — — 

Span/depth ratio of slab has been checked. — — — 

Adequacy of top and bottom reinforcement throughout slab panel has been checked. — — 

Designed to resist punching shear from columns. — 

Openings in slabs, especially near columns, have been designed for. — 

Torsional rigidity at slab edges has been checked. _ — 

Effects of construction loads have been checked. ... : 

Engineering 

drawings 

Clarity and consistency with the design intent of the architect and consultants, design bases and calculations, 
site surveys and investigations. — — — 

Complete sections and details. — — 

Consistency with and conformance to the specifications. — : : r— 

Consistency of the revisions and/or amendments to the design basis and criteria and their compliance with 
the design intent and Client requirement. 

Structural 

calculations 

Consistency of design loading with the criteria and the equipment supplier/vendors data, finishes, plus the 
possible construction method requirements, effects of foreseen temporary works and activities during 
construction, among others. — 

Usa«e of correct wind/seismic load parameters for analysis and design with regards to the structures lateral 
load resisting framing system, seismic zone, material type and structural framing plan or vertical ii regularity^ 

Seismic load analysis if requiring P-delta effects and/or dynamic method as to height limitations and 
irregularities. — — — 

Load combinations and special load combinations as required and prescribed by the code. __ 

Structural geometric model for completeness of the structures vertical load carrying elements and for 
consistency with the basis and criteria. _ — _ — — 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



IA-15 


Item 

Specific Design Checks to be Carried Out 


Member and element checks such as minimum reinforcements and details, strength requirements, 
slenderness effects, joints forces checks and connection requirements. 

Structural 

deformation 

and 

displacement 

checks 

Drift limitation of the structures (service and ultimate state). 

Size of movement joints or expansion joints. 

Girder and secondary beam deflections. 

Deformation compatibility on non-iateral load resisting elements. 

Stability/factors 
of safety check 

Overall and local structural stability against overturning and sliding. 

Compliance with factors of safety for miscellaneous requirements by clients. 

Earth retaining 
structures 

Structure has been designed to resist overturning, sliding and bearing capacity failure. 

Structure has been designed to resist slip circle failure. 

Structure has been designed for water pressure acting on it. 

Adequate surcharge load has been taken into account in design. 

Embedment into ground for stability has been designed for in cantilevered structures. 

Frame 

Check for type limitations if dual system, SMRF, etc. against height and materials. 

Checks for plan and vertical irregularities. 


Methodology and Details of Review 


The PR should agree with the Owner-Client and the BOR on the methodology of review. The review shall cover for 
completeness and timeliness of the design documents submitted per relevant items listed in this Guide. 

The PR should assess the review documents with regards to the agreed number of elements to be checked with the Owner- 
Client and/or his representative, if at random, selected or full review of the structure and any limited procedure. 

Review may be agreed also for each phase or entirely on the final detailed design phase of the structure for review. While a 
final detailed design review is basically economical, a phased review from the beginning may be better in order to avoid the 
errors from the beginning and save also valuable time in re-work. 

Design Basis Review 

The PR should do the following: 

1 . Review design criteria to verify compliance with the building code; 

2. Assess assumptions made by the EOR; and 

3. Review the proposed frame system/s and load path for vertical load-carrying elements. 


Recommended Guidelines on Structural Design 
Peer Review of Structures 2015 


IA-16 


Foundation Review 

The PR should do the following: 

1 

2 

or complexity of the project. 

3 . Review specification sections pertaining to foundation system including earthwork, piles, concrete work, among others. 

4. Review performance criteria for contractor-designed components such as slope protection systems, mini piles, tie-down 
anchors, among others. 

Pre-Tender Design Review 

The PR should carry out the following: 

1 Review structural framing connections which are part of the primary system including shear connections, braced frame 
Section "irienu-esfsting connections, among others. When connections are not detaded on the design drawmgs, 
verify adequacy of the cited connection design loads/procedures. 

2. Perform general review of design lo evaluate presence of any conditions which might precipitate instability or structural 
overstress. 

3. Review specification sections pertaining to Primary Structural Support System. 

4 Review performance criteria for contractor-designed components such as pre-cast concrete elements, shear connections, 
braced frame connections, moment-resisting connections, cold-formed metal framing components (primary ramii g 
components, not cladding), pre-engineered metal building systems, among otheis. 


Prior to the issuance of the final peer review report, the PR is encouraged to exchange review comments with the EOR in the 
presence of the Owner and/or his representative in order to resolve as many issues as possib e. 

Content 

The following items shall be included in the final peer review report: 


List of the documents on which the review was based; 

Building Codes and Standards on which the peer review was based; 
Methodology and assumptions of the review; 


1 . 

2 . 

3. 

4. List of software/analysis tools used with descriptive statements about software, tools and other computer programs used 
in the review; 


5. Items to be subsequently reviewed by others (e.g. contractor-designed items), 

6. Exclusions/limitations (e.g. peer review was limited to primary structural support systems), 

7. Outstanding items/unresolved issues; and 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


I A- 1 7 


8. Results, findings, conclusions and recommendations of the review. 

9. The final peer review report shall be addressed to the Owner-Client/representative and the EOR. Upon completion of the 
review, the PR shall issue a certificate stating that the peer review has been successfully completed 


Terms of Review Procedure and Methodology to be Used 

The review analysis and design criteria must meet the requirement of the Owner-Client as defined in his design brief including 
any applicable item in the Terms of Reference which form part of their agreement with the EOR. 

Preferably, the PR shall use the same design criteria and standards specified by the EOR. Deviations from the said criteria and 
standards must be done only with the permission of the EOR. 

Software to be used in the review should preferably be the same software used by the EOR (e.g. the same editions or versions). 
The difference of versions should be agreed upon but a difference of one level may be considered acceptable unless the more 
recent versions employ a different analysis procedures or features that are almost entirely different to the EOR’s software 
procedures or features. 


Language to be Used 

The manner of reporting shall always be factual. Numerical values and status to be presented must be taken purely from the 
final design review documents submitted and from the results of the independent review’s analysis and assessments per 
applicable codes and standards. 

The terms and phrases to be included in reporting any issue arising from the design review must be written carefully and reflect 
professionalism. The PR must not use offensive nor malicious words or phrases. Thus, the report must be factual and 
enlightening for the EOR and PR. 

The assessment of each part of the report should avoid terms like erroneous, in error and misses, among others. Reporting 
should preferably be neutral, for example, statement for bars needing additional quantity may be stated “underestimated” and 
bars in element with quantities that maybe reduced may be stated that “bars are overestimated by as much as 25%”. 

The PR shall make comments that are clear, legible and complete so that the EOR will easily understand it. Clear comments 
will eliminate confusion and reduce time spent in back-check. 


Mark-up and Comments 

Generally, comments should be complete, clear and legible. 

If possible, the PR should use words which would apply to numerous drawings so that the comments do not need to be repeated 
on each drawing. 

When the PR makes the same specific comments at many different details, the comments should be identified by either creating 
a standard, numbered list of comments with the comment numbers referenced at each detail, or by marking the comments on 
each detail. 

The PR may use 'paste-on 1 comments where applicable to save time and to maintain uniformity of comments. 


Recommended Guidelines on Structural Design 
Peer Review of Structures 2015 


IA-18 


Examples of Reviewer’s Comments/Wordings 

© Use specific comments such as: “ Show complete details In accordance with your calculation in pages 17 to 24. 

© Do not use vague comments such as: “ Clarify welding. " 

© Avoid personalized wording such as: “Your calculations for this connection is in error. 

© Provide code references for comments whenever possible: Provide additional lath support at horizontal soffits pet . . . 

© If the properties of an element were improperly used in calculations and the element is overstiessed, the PR should wiite 
a comment on the sheet where the overstressed element is shown such as:" W 18 x 36 overstressed. Recheck Section 
Modulus used in calculation. See AISC page.... and your calculation sheet F-l 9." 

© The PR can make independent calculations when portions of the design professional’s calculations are difficult to follow 
or interpret: “Shear wall is overstressed along Gridline- A, wall shears is in excess to allowable by 13 kN/m. " 

© If the PR does extensive independent calculations, then he or she must number the calculations in sequence and mark the 
calculation page number on the comment to facilitate the back-check: Composite beam overstressed \ recheck design loads . 
See page 28 . " 

References 

Association of Structural Engineers of the Philippines, Inc., Recommended Guidelines on Structural Design Peer Review of 
Structures. ASEP Committee on Design Peer Review 1999-2000 

Association of Structural Engineers of the Philippines, Inc., National Structural Code of the Philippines 1992 , Volume 1, 
Fourth Edition 

Association of Structural Engineers of the Philippines, Inc., National Structural Code of the Philippines 200 f Volume 1 , Fifth 
Edition 

Association of Structural Engineers of the Philippines, Inc., National Structural Code of the Philippines 2010, Volume 1, Sixth 
Edition 

American Council of Engineering Companies of Connecticut - Structural Engineers Coalition. Recommended Guidelines for 
Performing an Independent Structural Engineering Review in the State of Connecticut. Document SEC/CT301-08. 

American Concrete Institute, ACI 318 (2008). Building Code Requirements for Structural Concrete (AC! 318-08) and 
Commentary. 

American Society of Civil Engineers, ASCE 7 (2005), Minimum Design Loads for Buildings and Other Structures (ASCE/SEI 
7-05). 

American Society of Civil Engineers, Ethics : Guidelines for Professional Conduct for Civil Engineers. January 2008 
Autodesk, Inc., Revit Structure 2011 Users Guide . 

CTBUH 8 lh World Congress 2008, The Role of PR in the Foundation Design of the World’s Tallest Buildings , Baker, Kiefer, 
Nicoson and Fahoum. 

D. Matthew Stuart, Project Specific Peer Review Guidelines — A Professor Odyssey , Structure Magazine August 2010. 
International Code Council, Uniform Building Code 1997. 

IPENZ Practice Note 02, Peer Review - Reviewing the work of another Engineer. 

Pacific Earthquake Engineering Research Center Report No. 2010/05, Guidelines for Performance-Based Seismic Design of 
Tall Buildings , Version 1.0, November 2010. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



APPENDIX l-B - Guidelines and Implementing Rules on Earthquake Recording Instrumentation for Buildings I-B1 






I. INTRODUCTION 

Technology on building instrumentation for seismic 
monitoring has improved tremendously in the past decade. 
The purpose of this Guidelines and Implementing Rules on 
Earthquake Recording Instrumentation for Buildings is to 
provide information on the specifications and uses of 
earthquake recording instruments or buildings as provided 
in Section 105.2 of the National Structural Code of the 
Philippines 2010 Volume 1, Sixth Edition [NSCP 2010]. 

The Guidelines and Implementing Ruleson Earthquake 
Recording Instrumentation for Buildings provide 
earthquake instrumentation schemes for certain buildings 
to record building response during major seismic events for 
subsequent analysis. Adequate analysis of building 
response during earthquake is an important parameter in 
building safety evaluation in the confirmation and 
resumption of operations. 

Installation of earthquake recording instruments first 
appeared in the National Structural Code of the Philippines 
1992 Edition. At that period, structural engineers were 
mostly interested in the strength design capacity of the 
buildings based on seismic parameters provided in the 
Uniform Building Code (UBC) of the United States, a 
referral standard of the NSCP. This provision in the 1992 
NSCP, however, was not enforced. Code developers 
started to recognize the importance of not only strength but 
serviceability in buildings as well. The experiences from 
the 1994 Northridge Earthquake in the US and the 1995 
Kobe Earthquake in Japan gave credence to these 
considerations. 


adequate earthquake records have been obtained for 
various types of buildings or relevant provisions in the 
NSCP have been amended, the waiver stated above is 
temporarily suspended and buildings indicated in Table 1 
shall be provided with earthquake recording instruments. 

ASEP therefore deemed it necessary to improve our 
understanding of the building response based on real 
seismic event from local earthquake generators by 
promoting earthquake recording instrumentation for 
buildings as the NSCP provision was reiterated in the 200 1 
and 2010 Editions. Due to more recent developments in 
building instrumentation technology, a number of 
instrumentations are available to obtain the building 
response, and satisfy and comply with the objective of the 
NSCP Section 105 provisions. Hence, the requirement for 
three (3) accelerographs is further enhanced and modified 
to consider the latest and economical building instruments, 
thus, the combination or combinations of accelerographs, 
accelerometers, velocity meters and data loggers are 
considered. To measure building response due to long 
period earthquakes and distant sources normally critical to 
tall buildings, the addition of velocimeters is necessary. 

To further address the disaster management effort in the 
country, essential facilities such as hospitals and some 
government buildings, which are important facilities in 
disaster response, are recommended to be instrumented. In 
addition, with this new provision, building response from 
low-rise structures can be obtained to determine building 
behavior due to near source or short period earthquakes. 


The NSCP 2010 states that “ Unless waived by the building 
official , every building in Seismic Zone 4 over fifty (50) 
meters in height shall be provided with not less than three 
(3) approved recording accelerograph . The accelerograph 
shall be interconnected for common start and common 
timing Due to recent earthquakes and proliferation of 
high-rise buildings, the Philippines needs to have its own 
earthquake records for validating the seismic design 
parameters used, in order to support earthquake disaster 
mitigation / remedial efforts; thus, there is the need to 
implement the requirements for the earthquake recording 
instrumentation. Until such time that considerable sets of 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


I_B2 APPENDIX l-B - Guidelines and Implementing Rules on Earthquake Recording Instrumentation for Buildings 


IIL OBJECTIVES OF THESE GUIDELINES 

Section 102 of the National Building Code of the 
Philippines (PD 1096) states that “A is hereby declared to 
be the policy of the State to safeguard life , health , property, 
and public welfare, consistent with the principles of sound 
environmental management and control; and to this end, 
make it the purpose of this Code to provide for all buildings 
and structures , a framework of minimum standards and 
requirements to regulate and control their location, site , 
design, quality of materials, construction, use, occupancy, 
and maintenance .” 

In conformance thereto and as provided in the NSCP 2010, 
these Guidelines and Implementing Rules on Earthquake 
Recording Instrumentation for Buildings is developed to 
improve the understanding of the actual dynamic behavior 
of buildings under earthquake loading and confirm the 
design according to the NSCP. The recorded data can be 
used to improve the structural code thereby reducing loss 
of lives and limbs as well as properties during future 
damaging earthquakes. The response data from several 
buildings in a particular area or several areas will also be 
used as basis for the government’s earthquake disaster 
mitigation/remedial and rehabilitation strategies including 
its emergency response and relief operations programs. 
The instruments may also be used to set off alarms at 
specified intensity levels. They may also be used to trigger 
automatic switching off utilities such as gas lines, electric 
power lines and elevators as may be prudent in case of high 
intensity earthquake. The recorded data are important 
parameters for building safety re-evaluation and 
resumption of operations including post-earthquake 
evaluation of buildings. 


IV. DEFINITION OF TERMS 

ACCELEROGRAPH are acceierograph records the 
acceleration of particles on the surface of the earth as a 
function of time, which is called an accelerogram. The 
acceierograph generally records three mutually 
perpendicular components of motion in the vertical and 
two orthogonal horizontal directions. 

ACCELERATION is the rate at which the velocity of a 
particle changes with time. 

ACCELEROMETER is an instrument used to measure 
acceleration in the vertical and two orthogonal horizontal 
directions. An accelerometer has no built-in data recording 
capacity and is attached to a multi-channel data logger or 
an acceierograph to record measured acceleration. 

ACCREDITED STRUCTURAL ENGINEER (ASE) is 
a civil engineer with special qualifications to practice 
structural engineering with special training in earthquake 
engineering and certified by ASEP. 

ACTIONS (GROUND MOTION) is a general term 
including all aspects of ground motion, namely 
acceleration, velocity, or displacement from an earthquake 
or other energy source. 

BANDWIDTH is the frequency range that the sensor 
operates, measured in hertz. (Hz) 

CHANNEL is a path along which information (as data or 
voice) in the form of electrical signal, passes; a band of 
frequencies of sufficient width for a single radio or 
television communication. 

CLUSTERED BUILDINGS is a group of buildings built 
close together on a sizable tract of land in order to preserve 
open spaces larger than the individual yard for common 
recreation. 


DAMPING is the energy dissipation properties of a 
material or system under cyclic stress. 

DATA LOGGER is a data logger is an electronic device 
that records data over time or in relation to location either 
with a built in instrument or sensor or via external 
instruments and sensors. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


APPENDIX 1-B - Guidelines and Implementing Rules on Earthquake Recording Instrumentation for Buildings I-B3 


DISPLACEMENT is the measured distance travelled by 
a particle from an initial position. 

ENVIRONMENT is the aggregate of surrounding things, 
conditions, or influences that may affect the operability of 
an instrumentation device such as accelerograph, 
velocimeter, etc. 

ERL Earthquake Recording Instrumentations. 

FFT. Fast Fourier Transform (FFT) is a numerical 
algorithm to compute the discrete Fourier transform (DFT) 
and it’s inverse. Fourier analysis converts time to 
frequency and vice versa; an FFT rapidly computes such 
transformations by factorizing the DFT matrix into a 
product of sparse factors. 

GALS is the unit measure of acceleration equivalent to 
(!/1000)*g. Note that 1000 gals - Ig. 

g is acceleration due to gravity equals to 9.81 m/s 2 or 32.2 
ft/s 2 . 

INTENSITY is a number (written as a Roman numeral) 
describing the severity of an earthquake in terms of its 
effects on the earth’s surface and on humans and their 
structures. 

INTENSITY METER is an intensity meter records and 
stores the various data that are associated with the 
earthquake and that it can notify those data to host system 
as it equips data communication function. In addition, it 
makes the “Earthquake Early Warning System” workable 
with creating a system network by making use of optional 
“earthquake early detecting function.” 

IP67. The Ingress Protection rating system is a 
classification system showing the degrees of protection of 
the instrumentation device from solid objects and liquids. 
The first number refers to the protection against solid 
objects, normally dust. If the first number is 0, there is no 
protection provided. A number 5 refers to limited 
protection against dust. The number 6 is for total protection 
against dust. The second number of the IP rating system 
refers to protection against liquids. A “0” indicates no 
protection, while a “7” refers to protection against 
immersion between 15 cm to 1 m for 30 minutes. 


NATURAL FREQUENCY is the number of wave cycles 
per second which a system tends to oscillate in the absence 
of any driving or damping force. 

PEAK GROUND ACCELERATION [PGA] is the 
maximum ground acceleration at a specific location for the 
time interval. 

PERIOD is the time interval required for one full cycle of 
a wave, 

REFUGE AREA is an area inside a building where people 
evacuate or assemble during a disaster or emergency i.e. 
fire, but not for earthquake. 

RESPONSE SPECTRUM is a plot of the peak or 
amplitude of steady-state response (displacement, velocity 
or acceleration) of a series of oscillators of varying natural 
frequency that are forced into motion by the same base 
vibration or shock. 

SIR. Seismic Instrumentation Room. 

STRONG MOTION is a ground motion of sufficient 
amplitude to be of interest in evaluating the damage caused 
by earthquakes or nuclear explosions. 

TIME HISTORY is the sequence of values of any time- 
varying quantity (such as a ground motion measurement) 
reckoned at a set of [usually] equal time intervals. 

VELOCIMETER is an instrument used to measure 
velocity of a particle. 

VELOCITY is a measure of the rate of motion of a particle 
expressed as the rate of change of its position in a particular 
direction with time. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


I-B4 APPENDIX l-B - Guidelines and implementing Rules on Earthquake Recording Instrumentation for Buildings 

V. EARTHQUAKE RECORDING 

INSTRUMENTATION REQUIREMENTS 

The requirements of NSCP Section 105.2 shall apply to all 
existing buildings listed in Table 1, located in Seismic 
Zone 4 (entire Philippines except Palawan and Tawi- 
Tawi), for which certificates of occupancies were issued. 

Building permits shall only be issued for buildings 
qualified for seismic instrumentation when site or location 
of SIR has been indicated or incorporated in the plan. 


TABLE 1. EARTHQUAKE RECORDING INSTRUMENTATION REQUIREMENTS 

TYPE AND HEIGHT OF 
BUILDING 

LOCATION 

REQUIREMENTS 

GOVERNMENT BUILDINGS 

A. Hospitals, schools and 
other buildings fifty 
(50) meters high and 
above 

1 . Three (3) accelerographs at 
Ground Floor / Lowest 

Basement; Middle Floor; 
and Floor Below Roof, or 

2. One (1) accelerograph at 

Ground Floor / Lowest 

Basement interphased with 
two (2) accelerometers at 

Middle Floor and Floor 

Below Roof, or 

3. Three (3) accelerometers 
with common data logger 
at Ground Floor / Lowest 
Basement; Middle Floor; 
and Floor Below Roof 

1 . Accelerograph for 
recording waveform and 
transformed to FFT. 

2. Data output to include 
acceleration response 
spectra and pseudo 
acceleration response. 

3. With GPS capability. 

4. Capability to send data to 
data center of the 
government. 

B. Hospitals with 50-bed 
capacity or more and 

Schools with twenty 
(20) classrooms or more 
but not less than three 
(3) storey high 

One ( 1 ) accelerograph or one 
(1) accelerometer connected to 
a data logger, at Ground Floor/ 
Lowest Basement 

C. Provincial / City / 

Municipal Halls and 

Buildings 

One (1) accelerograph or one 
(1) accelerometer connected to 
a data logger, at Ground Floor 
Level/Lowest Basement 



Association of Structural Engineers of the Philippines. Inc. (ASEP) 



APPENDIX l~B - Guidelines and Implementing Rules on Earthquake Recording Instrumentation for Buildings I- 


TABLE 1. EARTHQUAKE RECORDING INSTRUMENTATION REQUIREMENTS (continued) 

type AND HEIGHT OF 
BUILDING 

LOCATION 

REQUIREMENTS 

PRIVATE BUILDINGS 

A. Buildings fifty (50) meters 
high and above 

1. Three (3) accelerographs at 
Ground Floor / Lowest 
Basement; Middle Floor; and 
Floor Below Roof, or 

2. One (1) accelerograph at 
Ground Floor / Lowest 
Basement interphase with two 
(2) accelerometers at Middle 
Floor and Floor Below Roof, or 

3. Three (3) accelerometers with 
common data logger at Ground 
Floor / Lowest Basement; 
Middle Floor; and Floor Below 
Roof 

1. Accelerograph for recording 
waveform and transformed to 
FFT. 

2. Data output to include 
acceleration response spectra 
and pseudo acceleration 
response. 

3. For buildings above ninety 
(90) meters or thirty (30) 
storeys in height, additional 
velocity meter at ground floor 
/ lowest basement shall be 
installed. Output data to 
include velocity response 
spectra and pseudo velocity 
response spectra. Data logger 
to be part of the system. 

4. With GPS capability. 

B. Hospitals with 50-bed 
capacity or more and 
Schools with 20 classrooms 
or more but not less than 
three (3) storey high 

One (1) accelerograph or one (!) 
accelerometer connected to a data 
logger at Ground Floor / Lowest 
Basement 

C. Commercial Buildings with 
occupancy of at least one 
thousand (1,000) persons or 
gross floor area of at least 
ten thousand (10,000) 
square meters 

One (1) accelerograph or one (1) 
accelerometer connected to a data 
logger at Ground Floor / Lowest 
Basement 


Table 1 shows the types of buildings required to be 
installed with earthquake recording instrumentation. The 
requirements for installation of accelerograph are for 
buildings located in cities and municipalities within a 200 
km radius from a Type A faults as specified in the NSCP 
2010 and as indicated from the active fault maps issued by 
the Philippine Institute of Seismology and Volcanology 
(PHIVOLCS). 


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I-B6 APPENDIX l-B - Guidelines and Implementing Rules on Earthquake Recording Instrumentation for Buildings 


For clustered buildings with completely similar design and 
construction, it shall have a minimum of eighteen (18) 
channels with a common data logger. The location of the 
instruments shall be determined by an Accredited 
Structural Engineer. 

1 . Maintenance . Earthquake Recording Instruments shall 
be maintained in proper working condition. The 
installation, servicing or removal of the instruments 
shall be done by qualified technical personnel of the 
supplier whose product complies with the minimum 
specifications as specified in these Guidelines and 
Implementing Rules. 

Maintenance of the instruments shall be by the owner 
of the building subject to the monitoring of the 
Building Official or its designated representative. 

2. Service Period. The maximum service interval is one 
(1) year. If the instrument is inoperative at two 
consecutive service inspections, then a re-inspection 
and servicing shall be required at a maximum service 
interval of six (6) months until the instrument is 
rendered fully operative. When the instrument 
continuously requires repair for a period of four (4) 
consecutive years, or inoperative repeatedly for at 
least three (3) times in a four (4)-year period, the 
instrument shall be replaced. 

3. Instrumentation of Selected Building . All owners of 
existing buildings listed in Table 1 shall provide 
accessible space for the installation of appropriate 
earthquake recording instruments. Location of said 
instruments shall be determined by an Accredited 
Structural Engineer. 

For proposed buildings, the Accredited Structural 
Engineer shall include the layout, instrument 
specifications, installation requirements, and location 
of the instrument in the structural plans submitted for 
building permit purposes. 

The actual installation of the instruments shall be 
verified by the Building Official. 

For existing buildings without ERI, the installation of 
these instruments shall form part of the requirements 
of the Annual Certificate of Inspection issued by the 
Building Official. 

For existing buildings with ERI, the building owner 
shall be required to submit a certification from ASE 
that the existing ERI conform to these guidelines. If 
the existing ERI do not conform to these guidelines, 
the building owner shall upgrade such ERI. 


For new buildings, the installation of these instruments 11 
shall form part of the requirements for Certificate of 8 
Occupancy issued by the Building Official. 

4. Additional Requisite Information of Buildings to be 
instrumented. It is necessary to establish a baseline 
data to make effective use of the records to be 
collected Rom the accelerograph(s) installed in the 
building. The following information are required: 

® As-built blueprints, 

© Structural design calculations, 

© Dynamic analysis (mode shapes and 
frequencies) as used in the design 
calculations, if available, forced-vibration 
test results, and ambient-vibration test 
results, and 

© Comprehensive subsurface soil exploration 
and investigation report. 

VI. DATA PROCESSING 

Modem strong motion instruments have capabilities to 

store and transmit digital data through telecommunications 

links and other media, including the internet. 

1 . The data from digital recordings are passed through a 
correction algorithm that applies a high-frequency 
filter (50 Hz typical: 1 Hz^l cycle per second). Plots 
of the corrected acceleration, velocity, and 
displacements for each channel of recording are 
prepared. 

2. Response spectra are calculated for periods up to about 
half of the long-period limit. Linear plots of relative- 
acceleration response spectra and plots of pseudo- 
acceleration response are prepared if specified to the 
instrument supplier. 

3. Fourier amplitude spectra, calculated by Fast Fourier ; 
Transform (FFT), are presented on linear axes and log- 
log axes. These sets of processed data are then i 
provided to the user for evaluation, assessment of | 
facilities and structures, and research. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


APPENDIX I-B - Guidelines and Implementing Rules on Earthquake Recording instrumentation for Buildings I-B7 


VIL STANDARD SPECIFICATIONS / 

REQUIREMENTS FOR EARTHQUAKE 
RECORDING INSTRUMENTS 

L The following are the minimum specifications for 
Earthquake Recording Instruments to be used for 
buildings listed in Table 1. 

A. Accelerographs/ Accelerometers: 

© Minimum design life: Ten (10) years and 
should be demonstrated and certified to have 
a 40,000-hour mean time (minimum) 
between failures. 

© Minimum of three (3) components - Vertical, 
Longitudinal and Transverse 

© Natural frequency: Above 50 Hz. 

© Damping: Approximately 60 to 70 percent 
critical. 

© Sensitivity: ±2000 gals or ±2g (full scale/V) 

© Bandwidth: DC to 100 Hz 
© Environment: IP67 or better 
© Input Range: ±2g - ±6g 

B. Velocimeters 

° Minimum of three (3) components - Vertical, 

Longitudinal and Transverse 

© Natural frequency: Above 50 Hz. 

© Damping: Approximately 60 to 70 percent 
critical. 

© Sensitivity: ±2 m/s 
0 Bandwidth: 0.1 Hz to 100 Hz 
© Environment: IP67 or better 

C. Data Logger / Recording. (Common for 
Accelerographs/Accelerometers and Velocimeters ) 

© Sampling Frequency: A minimum of 100 
samples per second. 

© Time: From at least 20 seconds before the 
ground shaking begins until 30 seconds after 
the last triggering level motion. 

© RMS Noise: System noise shall be less than 
40 jig’s measured over 0-30 Hz. 

© Media: Digital storage media (minimum of 
32 GB) 


© Continuous Monitoring: Capable for 
continuous recording by minimum one (1) 
year 

© AD converter: 24 bit or better. 

D. Timing. 

© Interval: Half second or less. 

© Accuracy: Plus or minus 0.2 second per 100 
seconds. 

© Type: GPS or NTP server. 

E. Triggering. 

© Method: Pendulum or other device using 
earthquake motion as exciting force. 

© Level: Accelerograph: 0.5 to 100 gals, 
nominal / Velocimeter: 0.005 mm/s to 1 
mm/s 

© Time: Full operation of accelerograph / 
velocimeter in not over 0.1 second after 
activation. 

F. Power. 

© Battery maintained by trickle charger from 
AC power and capable of powering the 
accelerograph and velocimeter for two (2) 
days after loss of power. 

G. Communication 

© Ethernet: 10 base-T or 100 base-TX 

© Protocol: TCP/IP FTP/SFTP 

2. Records. When media is used for recording, a 
new media load shall be placed in the instruments 
when the media remaining is less than 1/3 of 
original load. For instruments, memory should be 
copied out and emptied when the remaining 
amount is less than 1/3 of the original capacity. 

3. Refurbishing and Replacement. When the 
instrument supplier finds that the instrument must 
be removed from the building for repair, the 
instrument shall be replaced by a temporary 
identical instrument, and the permanent 
instrument shall be returned and made operative 
within 60 days from the removal date. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


I-B8 APPENDIX l-B - Guidelines and Implementing Rules on Earthquake Recording Instrumentation for Buildings 


4. Battery Inspection. The instrument shall be tested 
with any charge device disconnected from an 
electric power source. 

VIII. LOCATION AND INSTALLATION OF THE 
INSTRUMENTS 

1. General. 

The instrument shall be located so that access by 
qualified technical personnel is maintained at all times 
and is unobstructed by room contents. A sign stating 
“MAINTAIN CLEAR ACCESS TO THIS 
INSTRUMENT” shall be posted in a conspicuous 
location. No instruments shall be located in refuge 

area. 

The preferred locations of the instruments are in small, 
seldom-used rooms or closets near a column (in a 
vertically aligned stack), with adequate space to 
securely mount the instrument and an approved 
protective enclosure attached securely to the floor. The 
locations shall be marked on the submitted structural 
and architectural floor plans, and properly approved. 

2. Buildings with three (3) or more instruments. 

Buildings with three (3) or more 
accelerographs/accelerometers shall be located in the 
ground floor/lowest basement, middle floor, and the 
topmost floor of the building. When applicable, 
velocimeter shall be located in the lowest basement or 
ground floor level. The locations of the instruments are 
selected to provide the maximum information of the 
building response from a major earthquake. Such 
information would form part of the valuable data in 
understanding the building’s behavior during major 
seismic event. 

3. Orientation of the Instruments. 

All instruments shall be installed with the same 
orientation relative to the building, with the orientation 
chosen such that the reference or long dimension of 
the instrument is aligned with a major axis of the 
building. The orientation of the instrument shall be 
clearly marked on the submitted structural plans. The 
supplier-installer shall certify that the instruments are 
oriented as per plan. 


IX. DATA RETRIEVAL AND 
INTERPRETATION 

Immediately after the occurrence of an Intensity VI 
earthquake or greater in the locality as determined by 
the Philippine Institute of Volcanology and 
Seismology (PHIVOLCS), the Building Official shall 
issue a written notice to the building owner to retrieve 
the data and to have the data interpreted by an 
Accredited Structural Engineer. The retrieval and 
interpretation of the data shall be performed by an 
Accredited Structural Engineer. The data and 
interpretation of the building shall be submitted by the 
Owner to the DPWH for storage, post-earthquake 
safety evaluation of the building, and for emergency 
response. 

X. DATA STORAGE AND ARCHIVING 

Data storage and archiving shall be at the DPWH 
Central Office or other data centers designated by the 
DPWH. The ASEP, upon written request to the 
DPWH, shall be provided the said data. 

XL CERTIFICATE OF INSTALLATION OF 
EARTHQUAKE RECORDING 
INSTRUMENTATION 

Upon compliance of building owners of these 
Guidelines and Implementing Rules on Earthquake 
Recording Instrumentation, the Building Official shall 
issue a Certificate of Installation of Earthquake 
Recording Instrumentation. The Certificate must be 
posted at the room/s where the instrument is located 
and in a conspicuous place, properly 
protected/secured, in the ground floor lobby of the 
building. 

XII. TESTING, INSPECTION AND 
COMMISSIONING 

Building Owner, Building Official, and Supplier shall 
inspect, test, and commission the seismic monitoring 
system together to ensure that the systems are in 
proper operational condition and comply with the 
requirements of these guidelines. The Supplier must 
submit a certificate from the manufacturer that the 
instrument is in good working condition. 

The Building Owner shall be responsible for the 
protection and maintenance of the site of the ERI as 
prescribed in these guidelines. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


APPENDIX l-B - Guidelines and Implementing Rules on Earthquake Recording Instrumentation for Buildings l~B9 


XIII. SUPPORT AND MAINTENANCE 

The seismic monitoring system shall have a 
maintenance clearance as per the requirement of the 
National Structural Code of the Philippines under 
Section 105.2. ’’Maintenance and service shall be 
provided by the owner of the building.” 

"The supplier shall provide guarantee that the system 
shall have a maintenance period for at least 10 years. 
For the service period, the maximum service interval 
is one year. The equipment obsolescence shall not 
hinder the proper continuous operation of the 
equipment throughout the 10 years duration. When the 
equipment’s supplier finds that the instrument must be 
removed from the building for repair, there must be a 
service unit as a temporary replacement to continue 
the collection of data, if and when there is an 
occurrence of an earthquake during the duration of the 
repair. 

XIV. REFERENCES 


1. D Skolniket. al. A Quantitative Basis for Building 
Instrumentation Specifications , NSF CMMI Research 
and Innovation Conference, 2009 (Hawaii). 

2. M. Celebi. Seismic Instrumentation of Buildings: 
Special GSA/USGS PROJECT (2002). 

3. Guideline for ANSS Seismic Monitoring of 
Engineered Civil Systems - Version 1 .0. 

4. National Building Code of the Philippines, PD 1 096. 

5. National Structural Code of the Philippines (NSCP), 
Volume I, Buildings, Towers and Other Vertical 
Structures, Sixth Edition, 2010. 



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National Structural Code of the Philippines Volume I, 7th Edition, 2015 






CHAPTER 2 - Minimum Design Loads 2-1 


Table of Contents 

^SECTION 201 4 

general REQUIREMENTS 4 

201.1 Scope 4 

SECTION 202 4 

DEFINITIONS 4 

SECTION 203 10 

COMBINATIONS OF LOADS 10 

203.1 General 10 

203.2 Symbols and Notations 10 

203.3 Load Combinations using Strength Design or Load and Resistance Factor Design 11 

203.4 Load Combinations Using Allowable Stress or Allowable Strength Design 1 1 

203.5 Special Seismic Load Combinations 1 1 

SECTION 204 12 

DEAD LOADS 12 

204.1 General 12 

204.2 Weights of Materials and Constructions 12 

204.3 Partition Loads 12 

SECTION 205 15 

LIVE LOADS 15 

205.1 General 15 

205.2 Critical Distribution of Live Loads 15 

205.3 Floor Live Loads 1 5 

205.4 Roof Live Loads 19 

205.5 Reduction of Live Loads 19 

205.6 Alternate Floor Live Load Reduction 20 

Section 206 21 

OTHER MINIMUM LOADS 21 

206.1 General 21 

206.2 Other Loads 21 

206.3 Impact Loads 2 1 

206.4 Anchorage of Concrete and Masonry Walls 21 

206.5 Interior Wall Loads 2 1 

206.6 Retaining Walls 21 

206.7 Water Accumulation 21 

206.8 Uplift on Floors and Foundations 22 

206.9 Crane Loads 22 

206. 10 Heliport and Helistop Landing Areas 22 

SECTION 207 23 

WIND LOADS 23 

207. 1 Specifications 23 

2Q7 A General Requirements 23 

207 A. 1 Procedures 23 

207 A. 2 Definitions 25 

207A.3 Symbols and Notations 29 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-2 CHAPTER 2 - Minimum Design Loads 


207A.4 General * * 31 

207A.5 Wind Hazard Map 32 

207A.6 Wind Directionality 35 

207A.7 Exposure 36 

207 A. 8 Topographic Effects 46 

207A.9 Gust Effects 49 

207A.9.1 Gust Effect Factor 55 

207A.10 Enclosure Classification 57 

207A.1 1 Internal Pressure Coefficient 60 

207B Wind Loads On Buildings — MWFRS (Directional Procedure) 61 

207B.1 Scope * 61 

Part 1: Enclosed, Partially Enclosed, and Open Buildings of All Heights 62 

207B.2 General Requirements 62 

207 B ,3 Velocity Pressure 62 

207B.4 Wind Loads — Main Wind Force-Resisting System 68 

Part 2: Enclosed Simple Diaphragm Buildings with h — 48 m 82 

207B.5 General Requirements 32 

207B.6 Wind Loads — Main Wind Force-Resisting System 84 

207C Wind Loads On Buildings — MWFRS (Envelope Procedure) 1 04 

Part 1: Enclosed and Partially Enclosed Low-Rise Buildings 104 

207C.2 General Requirements 104 

207C.3 Velocity Pressure 105 

207C4 Wind Loads — Main Wind-Force Resisting System 109 

Part 2: Enclosed Simple Diaphragm Low-Rise Buildings 1 12 

207C.5 General Requirements 1 13 

207C.6 Wind Loads - Main Wind-Force Resisting System 114 

207D Wind Loads on Other Structures and Building Appurtenances - MWFRS 1 19 

207D.2 General Requirements 1 19 

207D.3 Velocity Pressure 1 19 

207D.4 Design Wind Loads - Solid Freestanding Walls and Solid Signs 122 

207D.5 Design Wind Loads — Other Structures 122 

207D.6 Parapets 123 

207D.8 Minimum Design Wind Loading 126 

207E Wind Loads - Components and Cladding (C&C) 130 

207E.1 Scope 130 

207E.2 General Requirements 132 

207E.3 Velocity Pressure 133 

Part 1: Low-Rise Buildings 136 

207E.4 Building Types 1 36 

Part 2: Low-Rise Buildings (Simplified) 137 

207E.5 Building Types 137 

Part 3: Buildings with h > 18 m * 139 

207E.6 Building Types * 1 39 

Part 4: Buildings with h < 48 m (Simplified) 140 

207E.7 Building Types 140 

Part 5: Open Buildings 155 

207E.8 Building Types ... 155 

Part 6: Building Appurtenances and Rooftop Structures and Equipment 1 56 

207E.9 Parapets * * 1 56 

207E.10 Roof Overhangs 157 

207E.1 1 Rooftop Structures and Equipment for Buildings with h < 18 m 158 

207F Wind Tunnel Procedure 180 

SECTION 208 184 

EARTHQUAKE LOADS 184 

208.1 General 184 

Association of Structural Engineers of the Philippines, Inc. (ASEP) 


jpj mm 


CHAPTER 2 - Minimum Design Loads 2-3 


K208.2 Definitions 

208.3 Symbols and Notations jg 4 

i'208.4 Basis for Design j 85 

£ 208,5 Minimum Design Lateral Forces and Related Effects 212 

. 208.6 Earthquake Loads and Modeling Requirements 219 

v 208.7 Detailed Systems Design Requirements 221 

; 208.8 Non-Building Structures 229 

208.9 Lateral Force on Elements of Structures, Nonstructural Components and Equipment Supported by Structures 231 

208.10 Alternative Earthquake Load Procedure 


184 


236 


SECTION 209. 


SOIL LATERAL LOADS 

209.1 General 

SECTION 2 10 

RAIN LOADS ->•><> 


210.1 Roof Drainage 

210.2 Design Rain Loads 

210.3 Ponding Instability 

210.4 Controlled Drainage 


SECTION 211. 


i FLOOD LOADS. 


General 

Definitions 

Design Requirements 

Loads During Flooding 

Establishment of Flood Hazard Areas 

Design and Construction 

Flood Hazard Documentation 

Consensus Standards and Other Referenced Documents 




National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-4 CHAPTER 2 - Minimum Design Loads 


SECTION 201' 

general jmtMmmxMmmm 



201.1 Scope 

This chapter provides minimum design load requirements 
for the design of buildings, towers and other vertical 
structures. Loads and appropriate load combinations which 
have been developed to be used together for strength 
design and allowable stress design are set forth. 



SECTION 202 
^DEFINITIONS 

The following terms are defined for use in this section: 

ACCESS FLOOR SYSTEM is an assembly consisting of 
panels mounted on pedestals to provide an under-floor 
space for the installation of mechanical, electrical, 
communication or similar systems or to serve as an air- 
supply or return-air plenum. 

AGRICULTURAL BUILDING is a structure designed 
and constructed to house farm implements, hay, giain, 
poultry, livestock or other horticultural products. The 
structure shall not be a place of human habitation or a place 
of employment where agricultural products are processed, 
treated, or packaged, nor shall it be a place used by the 
public. 

ALLOWABLE STRESS DESIGN (ASD) is a method of 
proportioning and designing structural members such that 
elastically computed stresses produced in the members by 
nominal loads do not exceed specified allowable stresses 
(also called working stress design). 

ASSEMBLY BUILDING is a building or portion of a 
building for the gathering together of 50 or more persons 
for such purposes as deliberation, education, instruction, 
worship, entertainment, amusement, drinking or dining, or 
awaiting transportation. 

AWNING is an architectural projection that provides 
weather protection, identity, or decoration and is wholly 
supported by the building to which it is attached. 

BALCONY, EXTERIOR, is an exterior floor system 
projecting from and supported by a structure without 
additional independent supports. 

BASE is the level at which the earthquake motions are 
considered to be imparted to the structure or the level at 
which the structure, as a dynamic vibrator, is supported. 

BASE SHEAR is the total design lateral force or shear at 
the base of a structure. 

BASIC WIND SPEED is a three-second gust speed at 10 
m above the ground in Exposure C (see Section 207 A. 7. 3) 
as determined in accordance with Section 207A.5.1 and 
associated with an annual probability of 0.02, (i.e. 50-year 
mean recurrence interval). 

BEARING WALL SYSTEM is a structural system that 
does not have a complete vertical load-carrying space 
frame. See Section 208.4.6.1. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-5 


BOUNDARY ELEMENT is an element at edges of 
openings or at perimeters of shear walls or diaphragms. 

BRACED FRAME is essentially a vertical truss system of 
the concentric or eccentric type that is provided to resist 
lateral forces. 


BUILDING FRAME SYSTEM is essentially a complete 
space frame that provides support for gravity loads. See 
Section 208.4.6.2. 


BRACED WALL LINE is a series of braced wall panels 
in a single storey that meets the requirements of Section 
620.10.3. 

BRACED WALL PANEL is a section of wail braced in 
accordance with Section 620.10.3. 


BUILDING, ENCLOSED is a building that does not 
comply with the requirements for open or partially 
enclosed buildings. 

BUILDING ENVELOPE refers to cladding, roofing, 
exterior wall, glazing, door assemblies, window 
assemblies, skylight assemblies, and other components 
enclosing the building. 

BUILDING, FLEXIBLE refers to slender buildings that 
Have a fundamental natural frequency less than 1.0 Hz. 


BUILDING, LOW-RISE is an enclosed or partially 
enclosed building that complies with the following 
conditions: 

1 . Mean roof height, ft, less than or equal to 1 8m, and 

2. Mean roof height, ft, does not exceed least horizontal 
||f dimension. 

BUILDING, OPEN refers to a building having each wall 
at least 80 percent open. This condition is expressed for 
each wall by the equation A 0 > 0. 8A g . See symbols and 
notations. 

BUILDING, PARTIALLY ENCLOSED is a building 
that complies with both of the following conditions: 

1. the total area of openings in a wall that receives 
positive external pressure exceeds the sum of the areas 
of openings in the balance of the building envelope 
||f (walls and roof) by more than 10%; and 


2. The total area of openings in a wall that receives 
positive external pressure exceeds 0.5 m 2 or 1 percent 
lf : of the area of that wall, whichever is smaller, and the 




percentage of openings in the balance of the building 
envelope does not exceed 20 percent. 

These conditions are expressed by the following equations: 

1. A 0 > 1. 10A O [ 

2. A 0 > smaller of (0, 5 m 2 or 0. 01A g ) 

3- A oi /A %i < 0.20 

See symbols and notations. 

BUILDING OR OTHER STRUCTURE, REGULAR- 
SHAPED refers to a building or other structure having no 
unusual geometrical irregularity in spatial form. 

BUILDING OR OTHER STRUCTURES, RIGID refer 
to a building or other structure whose fundamental 
frequency is greater than or equal to 1 .0 Hz. 

BUILDING, SIMPLE DIAPHRAGM refers to a 
building in which both windward and leeward wind loads 
are transmitted through floor and roof diaphragms to the 
same vertical MWFRS (e.g., no structural separations). 

CANTILEVERED COLUMN ELEMENT is a column 
element in a lateral-force-resisting system that cantilevers 
from a fixed base and has minimal moment capacity at the 
top, with lateral forces applied essentially at the top. 

COLLECTOR is a member or element provided to 
transfer lateral forces from a portion of a structure to 
vertical elements of the lateral-force-resisting system. 

COMPONENT is a part or element of an architectural, 
electrical, mechanical or structural system. 

COMPONENT, EQUIPMENT is a mechanical or 
electrical component or element that is part of a mechanical 
and/or electrical system. 

COMPONENT, FLEXIBLE is a component, including 
its attachments, having a fundamental period greater than 
0.06 s. 

COMPONENT, RIGID is a component, including its 
attachments, having a fundamental period less than or 
equal to 0.06s. 

COMPONENTS AND CLADDING refers to elements of 
the building envelope that do not qualify as part of the 
MWFRS. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-6 CHAPTER 2 - Minimum Design Loads 

CONCENTRICALLY-BRACED FRAME is a braced 
frame in which the members are subjected primarily to 
axial forces. 

CONVENTIONAL LIGHT-FRAME 

CONSTRUCTION is a type of construction in which the 
primary structural elements are formed by a system of 
repetitive wood framing members. 

COVERING, IMPACT-RESISTANT is a covering 
designed to protect impact-resistant glazing. 

CRIPPLE WALL is a framed stud wall extending from 
the top of the foundation to the underside of floor framing 
for the lowest occupied level. 

DEAD LOADS consist of the weight of all materials and 
fixed equipment incorporated into the building or other 
structure. 

DECK is an exterior floor system supported on at least two 
opposing sides by an adjacent structure and/or posts, piers, 
or other independent supports. 

DESIGN BASIS GROUND MOTION is that ground 
motion that has a 10 percent chance of being exceeded in 
50 years as determined by a site-specific hazard analysis or 
may be determined from a hazard map. 

DESIGN FORCE is the equivalent static force to be used 
in the determination of wind loads for open buildings and 
other structures. 

DESIGN RESPONSE SPECTRUM is an elastic 
response spectrum for 5 percent equivalent viscous 
damping used to represent the dynamic effects of the 
Design Basis Ground Motion for the design of structures in 
accordance with Sections 20S.5 and 208.5.3. 

DESIGN SEISMIC FORCE is the minimum total 
strength design base shear, factored and distributed in 
accordance with Section 208.5. 

DESIGN PRESSURE is the equivalent static pressure to 
be used in the determination of wind loads for buildings. 

DIAPHRAGM is a horizontal or nearly horizontal system 
acting to transmit lateral forces to the vertical resisting 
elements. The term "diaphragm" includes horizontal 
bracing systems. 

DIAPHRAGM, BLOCKED is a diaphragm in which all 
sheathing edges not occurring on framing members are 
supported on and connected to blocking. 


DIAPHRAGM CHORD or SHEAR WALL CHORD is 
the boundary element of a diaphragm or shear wall that is 
assumed to take axial stresses analogous to the flanges of a 
beam. 

DIAPHRAGM STRUT (drag strut, tie, and collector) is 
the element of a diaphragm parallel to the applied load that 
collects and transfers diaphragm shear to the vertical 
resisting elements or distributes loads within the 
diaphragm. Such members may take axial tension or 
compression. 

DIAPHRAGM, UNBLOCKED is a diaphragm that has 
edge nailing at supporting members only. Blocking 
between supporting structural members at panel edges is 
not included. 

DRIFT or STOREY DRIFT is the lateral displacement of 
one level relative to the level above or below. 

DUAL SYSTEM is a combination of moment-resisting 
frames and shear walls or braced frames designed in 
accordance with the criteria of Section 208.4.6.4. 



EAVE HEIGHT is the distance from the ground surface 
adjacent to the building to the roof eave line at a particular 
wall. If the height of the eave varies along the wall, the 
average height shall be used. 

ECCENTRICALLY BRACED FRAME (EBF) is a 
steel-braced frame designed in conformance with Section 
528. 

EFFECTIVE WIND AREA is the area used to determine 
GC p . For cladding fasteners, the effective wind area shall 
not be greater than the area that is tributary to an individual 
fastener. 

ELASTIC RESPONSE PARAMETERS are forces and 
deformations determined from an elastic dynamic analysis 
using an unreduced ground motion representation, in 
accordance with Section 208.5.3. 

ESCARPMENT, also known as scarp, with respect to 
topographic effect in Section 207 A.8, is a cliff or steep 
Mope generally separating two levels or gently sloping 
areas (see Figure 207A-8-1). 



ESSENTIAL FACILITIES are buildings, towers and 
other vertical structures that are intended to remain 
operational in the event of extreme environmental loading | 
from wind or earthquakes. 


FACTORED LOAD is the product of a load specified in 
Sections 204 through 208 and a load factor. See Section 
203.3 for combinations of factored loads. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-7 


FIBERBOARD is a fibrous, homogeneous panel made 
from lignocellulosic fibers (usually wood or sugar cane 
bagasse) and having a density of less than 50 kg/m 3 but 
more than 160 kg/m 3 . 

FLEXIBLE ELEMENT or SYSTEM is one whose 
deformation under lateral load is significantly larger than 
adjoining parts of the system. Limiting ratios for defining 
specific flexible elements are set forth in Section 208. 5. 1 .3. 

forest products research and 

DEVELOPMENT INSTITUTE (FPRDI) is the 
Department of Science and Technology’s (DOST’s) 
research and development arm on forest products 
utilization. It is mandated to conduct basic and applied 
research to help the wood-using industries disseminate 
information and technologies on forest products to end 
users. 

FREE ROOF is a roof with a configuration generally 
conforming to those shown in Figures 207B.4-4 through 
207B.4-6 (monoslope, pitched, or troughed) in an open 
building with no enclosing walls underneath the roof 
surface. 

GARAGE is a building or portion thereof in which motor 
vehicle containing flammable or combustible liquids or gas 
in its tank is stored, repaired or kept. 

GARAGE, PRIVATE, is a building or a portion of a 
building, not more than 90m 2 in area, in which only motor 
vehicles used by the tenants of the building or buildings on 
the premises are kept or stored. 

GLAZING is a glass or transparent or translucent plastic 
sheet used in windows, doors, skylights, or curtain walls. 

GLAZING, IMPACT-RESISTANT is a glazing that has 
been tested in accordance with ASTM El 886 and ASTM 
El 996 or other approved test methods to withstand the 
impact of wind-borne missiles likely to be generated in 
wind-borne debris regions during design winds. 

GLUED BUILT-UP MEMBERS are structural elements, 
the section of which is composed of built-up lumber, wood 
structural panels or wood structural panels in combination 
with lumber, all parts bonded together with structural 
adhesives. 


GRADE (LUMBER) is the classification of lumber in 
regard to strength and utility in accordance with the 
grading rules of an approved lumber grading agency. 


HARDBOARD is a fibrous-felted, homogeneous panel 
made from lignocellulosic fibers consolidated under heat 
and pressure in a hot press to a density not less than 
50kg/m 3 . 

HILL, with respect to topographic effects in Section 
207A.8, is a land surface characterized by strong relief in 
any horizontal direction (Figure 207A.8-2). 

HORIZONTAL BRACING SYSTEM is a horizontal 
truss system that serves the same function as a diaphragm. 

IMPACT-RESISTANT COVERING, is a covering 
designed to protect glazing, which has been shown by 
testing in accordance with ASTM El 886 and ASTM 
El 996 of other approved test methods to withstand the 
impact or wind-borne debris missiles likely to be generated 
in wind-borne debris regions during design winds. 

IMPORTANCE FACTOR is a factor that accounts for 
the degree of hazard to human life and damage to property. 

INTERMEDIATE MOMENT RESISTING FRAME 
(IMRF) is a concrete frame designed in accordance with 
Section 412. 

LATERAL-FORCE-RESISTING SYSTEM is that part 
of the structural system designed to resist the Design 
Seismic Forces. 

LIMIT STATE is a condition beyond which a structure or 
member becomes unfit for service and is judged to be no 
longer useful for its intended function (serviceability limit 
state) or to be unsafe (strength limit state). 

LIVE LOADS are those loads produced by the use and 
occupancy of the building or other structure and do not 
include dead load, construction load, or environmental 
loads. 

LOADS are forces or other actions that result from the 
weight of all building materials, occupants and their 
possessions, environmental effects, differential 
movements, and restrained dimensional changes. 
Permanent loads are those loads in which variations over 
time are rare or of small magnitude. All other loads are 
variable loads. 

LOAD AND RESISTANCE FACTOR DESIGN 
(LRFD) METHOD is a method of proportioning and 
designing structural elements using load and resistance 
factors such that no applicable limit state is reached when 
the structure is subjected to all appropriate load 
combinations. The term ”LRFD M is used in the design of 
steel structures. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-8 CHAPTER 2 - Minimum Design Loads 


MACHINE-GRADED LUMBER (MGL) is a lumber 
evaluated by a machine using a non-destructive test and 
sorted into different stress grades. 

MAIN WIND-FORCE RESISTING SYSTEM 
(MWFRS) is an assemblage of structural elements 
assigned to provide support and stability for the overall 
structure. The system generally receives wind loading from 
more than one surface. 

MARQUEE is a permanent roofed structure attached to 
and supported by the building and projecting over public 
right-of-way. 

MEAN ROOF HEIGHT is the average of the roof eave 
height and the height to the highest point on the roof 
surface, except that, for roof angles of less than or equal to 
10°, the mean roof height shall be the roof eave height. 

MOISTURE CONTENT (MC) is the amount of moisture 
in wood, usually measured as the percentage of water to the 
oven dry weight of the wood. 

MOMENT-RESISTING FRAME is a frame in which 
members and joints are capable of resisting forces 
primarily by flexure. 

MOMENT-RESISTING WALL FRAME (MRWF) is a 
masonry wall frame especially detailed to provide ductile 
behavior and designed in conformance with Section 
708.2.6. 

NOMINAL LOADING is a design load that stressed a 
member or fastening to the full allowable stress tabulated 
in this chapter. This loading may be applied for 
approximately 10 years, either continuously or 
cumulatively, and 90 percent of this load may be applied 
for the remainder of the life of the member or fastening. 

NOMINAL SIZE (Lumber) refers to the commercial size 
designation of width and depth, in standard sawn lumber 
and glued laminated lumber grades; somewhat larger than 
the standard net size of dressed lumber. 

OPENINGS are apertures or holes in the building 
envelope that allow air to flow through the building 
envelope and that are designed as “open” during design 
winds as defined by these provisions. 

ORDINARY BRACED FRAME (OBF) is a steel-braced 
frame designed in accordance with the provisions of 
Section 527 or 528 or concrete-braced frame designed in 
accordance with Section 42 1 . 



ORDINARY MOMENT-RESISTING FRAME 
(OMRF) is a moment-resisting frame not meeting special 
detailing requirements for ductile behavior. 

ORTHOGONAL EFFECTS are the earthquake load 
effects on structural elements simultaneously occurring to 
the lateral-fbrce-resisting systems along two orthogonal 
axes. vj 

OVERSTRENGTH is a characteristic of structures where -| 
the actual strength is larger than the design strength. The 1 
degree of over-strength is material-and system-dependent 

PARTICLEBOARD is a manufactured panel product 
consisting of particles of wood or combinations of wood 
particles and wood fibers bonded together with synthetic f|j 
resins or other suitable bonding system by a bonding j 
process, in accordance with approved nationally 
recognized standard. 

PLYWOOD is a panel of laminated veneers conforming 
to Philippine National Standards (PNS 196) “Plywood 
Specifications”. 

PA EFFECT is the secondary effect on shears, axial forces 
and moments of frame members induced by the horizontal 
displacement of vertical loads from various loading, when - 
a structure is subjected to lateral forces. 

RECOGNIZED LITERATURE are published research | 
findings and technical papers that are approved. 

RIDGE, with respect to topographic effects in Section | 
207 A.8, is an elongated crest of a hill characterized by 
strong relief in two directions (see Figure 207A.8-1). 

ROTATION is the torsional movement of a diaphragm 
about a vertical axis. 

SHEAR WALL is a wall designed to resist lateral forces 
parallel to the plane of the wall (sometimes referred to as 
vertical diaphragm or structural wall). 

SHEAR WALL-FRAME INTERACTIVE SYSTEIVt| 
uses combinations of shear walls and frames designed to| 
resist lateral forces in proportion to their relative rigidities, 
considering interaction between shear walls and frames on 
all levels. ' 


Association of Structural Engineers of the Philippines, Inc. (ASCP) 


CHAPTER 2 - Minimum Design Loads 2-9 


SHEATHING is a layer of boards or of other wood or fiber 
materials applied to the outer studs, joists, and rafters of a 
building to strengthen structures and serve as a base for an 
exterior weatherproof cladding. 

SHEATHING, WALL is a layer of boards or of other 
wood or fiber materials used to cover the wall studding. 


STRUCTURAL GLUED-LAMINATED TIMBER is 
any member comprising an assembly of laminations of 
lumber in which the grain of all laminations is 
approximately parallel longitudinally, in which the 
laminations are bonded with adhesives. 

SUBDIAPHRAGM is a portion of a diaphragm used to 
transfer wall anchorage forces to diaphragm cross ties. It 
also refers to a portion of a larger wood diaphragm 
designed to anchor and transfer local forces to primary 
diaphragm struts and the main diaphragm. 

SOFT STOREY is one in which the lateral stiffness is less 
than 70 percent of the stiffness of the storey above. See 
Table 208-9. 

SPACE FRAME is a three-dimensional structural system, 
without bearing walls, composed of members 
interconnected so as to function as a complete self- 
contained unit with or without the aid of horizontal 
diaphragms or floor-bracing systems. 

SPECIAL CONCENTRICALLY BRACED FRAME 
(SCBF) is a steel-braced frame designed in conformance 
with the provisions of Section 526. 

SPECIAL MOMENT-RESISTING FRAME (SMRF) 
is a moment-resisting frame specially detailed to provide 
ductile behavior and comply with the requirements given 
in Chapter 4 or 5. 

SPECIAL TRUSS-MOMENT FRAME (STMF) is a 
moment-resisting frame specially detailed to provide 
ductile behavior and comply with the provisions of Section 
525. 

STOREY is the space between levels. Storey x is the 
storey below level x. 

STOREY DRIFT RATIO is the storey drift divided by 
the storey height. 

STOREY SHEAR, V x , is the summation of design lateral 
forces above the storey under consideration. 

STRENGTH is the capacity of an element or a member to 
resist factored load as specified in Chapters 2, 3, 4, 5 and 


STRUCTURE is an assemblage of framing members 
designed to support gravity loads and resist lateral forces. 
Structures may be categorized as building structures or 
nonbuilding structures. 

STRENGTH DESIGN is a method of proportioning and 
designing structural members such that the computed 
forces produced in the members by the factored load do not 
exceed the member design strength. The term strength 
design is used in the design of concrete structures. 

TOWERS AND OTHER STRUCTURES are 
nonbuilding structures including poles, masts and 
billboards that are not typically occupied by persons but are 
also covered by this code. 

TREATED WOOD is wood treated with an approved 
preservative under treating and quality control procedures. 

VERTICAL LOAD-CARRYING FRAME is a space 
frame designed to carry vertical gravity loads. 

WALL ANCHORAGE SYSTEM is the system of 
elements anchoring the wall to the diaphragm and those 
elements within the diaphragm required to develop the 
anchorage forces, including sub-diaphragms and 
continuous ties, as specified in Sections 208.7.2.7 and 
208.7.2.8. 

WALL, BEARING is any wall meeting either of the 
following classifications: 

1. Any metal or wood stud wall that supports more than 
1.45 kN/m of vertical load in addition to its own 
weight. 

2. Any masonry or concrete wall that supports more than 
2.90 kN/m of vertical load in addition to its own 
weight. 

WALL, EXTERIOR is any wall or element of a wall, or 
any member or group of members, that defines the exterior 
boundaries or courts of a building and that has a slope of 
60 degrees or greater with the horizontal plane. 

WALL, NONBEARING is any wall that is not a bearing 
wall. 

WALL, P ARAPET is that part of any wall entirely above 
the roof line. 

WALL, RETAINING is a wall designed to resist the 
lateral displacement of soil or other materials. 

WEAK STOREY is one in which the storey strength is 
less than 80 percent of the storey above. See Table 208-9. 


National Structural Code of the Philippines Volume l, 7th Edition, 2015 


2-10 CHAPTER 2 - Minimum Design Loads 


WIND-BORNE DEBRIS REGIONS are areas within 
typhoon prone regions located at: 

1. Within 1.6 km of the coastal mean high water line 
where the basic wind speed is equal to or greater than 
200 kph, or 

2. In areas where the basic wind speed is equal to or 
greater than 250 kph. 

WOOD OF NATURAL RESISTANCE TO DECAY 
OR TERMITES is the heartwood of the species set forth 
below. Corner sapwood is permitted on 5 percent of the 
pieces provided 90 percent or more of the width of each 
side on which it occurs is heartwood. Recognized species 
are: 

o Decay resistant: Narra, Kamagong, Dao, Tangile. 
o Termite resistant: Narra, Kamagong. 

WOOD STRUCTURAL PANEL is a structural panel 
product composed primarily of wood and meeting the UBC 
Standard 23-2 and 23-3 or equivalent requirements of 
Philippine National Standards (PNS). Wood structural 
panels include all-veneer plywood, composite panels 
containing a combination of veneer and wood-based 
material, and mat-formed panel such as oriented stranded 
board and wafer board. 


WYTHE is the portion of a wall which is one masonry unit 
in thickness. A collar joint is not considered a wythe. 



;S>K@XlOJft : 2’03 N NMS:KI§8111i 

COMBINATIONS OS-’ LOADS 

203.1 General 

Buildings, towers and other vertical structures and all 
portions thereof shall be designed to resist the load 
combinations specified in Section 203.3, 203.4 and 203.5. 

The most critical effect can occur when one or more of the 
contributing loads are not acting. All applicable loads shall 
be considered, including both earthquake and wind, in 
accordance with the specified load combinations. 

203.2 Symbols and Notations 

D = dead load 

E = earthquake load set forth in Section 208.6. 1 
E m = estimated maximum earthquake force that 

can be developed in the structure as set forth 
in Section 208.6. 1 

F = load due to fluids with well-defined 
pressures and maximum heights 
H = load due to lateral pressure of soil and water 
in soil 

i = live load, except roof live load, including 
any permitted live load reduction 
L r = roof live load, including any permitted live 
load reduction 
P = ponding load 

R - rain load on the undeflected roof 
T = self-straining force and effects arising from 
contraction or expansion resulting from 
temperature change, shrinkage, moisture 
change, creep in component materials, 
movement due to differential settlement, or 
combinations thereof 
W = load due to wind pressure 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 









jgf|3.3 Load Combinations using Strength Design or 
Load and Resistance Factor Design 

;203.3.t Basic Load Combinations 

Inhere strength design or load and resistance factor design 
its used, structures and all portions thereof shall resist the 
§j||st critical effects from the following combinations of 
f factored loads: 


. 


gf:1.4(D + F) (203-1) 

£’■1.2(0 + F + r) + 1.6(L + H) 

+ 0. 5 (L r or R) (20i ' 2) 

«1, 2D + 1. 6(L r or R ) + (f t L or 0. 5 W) (203-3) 
|p 1.20 + 1.0W + f t L + 0. 5(L r or R') (203-4) 

M 1. 20 + 1. 0 E + f l L (203-5) 

0.90 + 1. OW + 1.60 (203-6) 

Ife 0.90 + 1.0E+ 1.60 (203-7) 


1.2(D + F + T) + 1.6(L + H) 

+ 0. 5(L r or R) 


here 



1.0 for floors in places of public assembly, 
for live loads in excess of 4.8 kPa, and for 
garage live load, or 

0.5 for other live loads 

2(13.3.2 

Other Loads 

jjjjjJ||fcWhere P is to be considered in design, the applicable load 
be added to Section 203.3.1 factored as 1. 2 P. 


203.4 Load Combinations Using Allowable Stress or 
Allowable Strength Design 

|i203.4. 1 Basic Load Combinations 

Where allowable stress or allowable strength design is 
structures and all portions thereof shall resist the most 
^critical effects resulting from the following combinations 
of loads: 

D + F (203-8) 

: : D + H + F + L + T (203-9) 

D + H + F + (L r or R) (203-10) 

D + U + F+ 0. 75[L + T(L r or R)] (203-1 1 ) 

n , rr , r, . E \ 


CHAPTER 2 - Minimum Design Loads 2-1 1 


No increase in allowable stresses shall be used with these 
load combinations except as specifically permitted by 
Section 203.4.2. 

203.4.2 Alternate Basic Load Combinations 

In lieu of the basic load combinations specified in Section 
203.4.1, structures and portions thereof shall be permitted 
to be designed for the most critical effects resulting from 
the following load combinations. When using these 
alternate basic load combinations, a one-third increase 
shall be permitted in allowable stresses for all 
combinations, including W or E. 



D + H + F + 0. 75 L + L r (o.6W or 

(203-13) 

(203-3) 



0.6D + 0.6W+ H 

(203-14) 

(203-4) 

E 



0. 6D + — - + H 

1.4 

(203-15) 

(203-5) 


(203-6) 

D + L + (JL r or /?) 

(203-16) 

D + L + 0.6W 

(203-17) 

(203-7) 

E 



D+L+ n 

(203-18) 


Exception: 

Crane hook loads need not be combined with roof live load 
or with more than one-half of the wind load. 

203.4.3 Other Loads 

Where P is to be considered in design, each applicable load 
shall be added to the combinations specified in Sections 
203.4.1 and 203.4.2. 

203.5 Special Seismic Load Combinations 

For both allowable stress design and strength design for 
concrete, and Load and Resistance Factor Design (LRFD) 
and Allowable Strength Design (ASD) for steel, the 
following special load combinations for seismic design 
shall be used as specifically required by Section 208, or by 
Chapters 3 through 7. 

1. 2D -h L + 1. 0E m (203-19) 

0. 9D ± 1. 0E m (203-20) 


D + // + p + ( 0 . 6W or 


(203-12) 


National Structural Code of the Philippines Volume L 7th Edition, 2015 


2-12 CHAPTER 2 - Minimum Design Loads 



where 

/j = 1.0 for floors in places of public assembly, 

for live loads in excess of 4.8 kPa, and for 
garage live load, or 
= 0.5 for other live loads 

£ = the maximum effect of horizontal and 

vertical forces as set forth in Section 208.6.1 




SEC TION 204 

lll gi ffililsl g illl llii 

204.1 General 

|| 

Dead loads consist of the weight of all materials de- 
construction incorporated into the building or othefe^B 
structure, including but not limited to walls, floors, roots. | J 
ceilings, stairways, built-in partitions, finishes, cladding > 
and other similarly incorporated architectural an djjj 
structural items, and fixed service equipment, including the || 
weight of cranes. 

204.2 Weights of Materials and Constructions 

up 

The actual weights of materials and constructions shall bejj 
used in determining dead loads for purposes of design. Injj 
the absence of definite information, it shall be permitted to : 
use the minimum values in Tables 204-1 and 204-2. 

204.3 Partition Loads 

Floors in office buildings and other buildings wher|J 
partition locations are subject to change shall be designed^ 
to support, in addition to all other loads, a uniformlygj 
distributed dead load equal to 1.0 kPa. 

Exception: 

Access floor systems shall be designed to support .WiL 
addition to all other loads, a uniformly distributed jjj 
load not less than 0.5 kPa. 


J| 

I 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-13 


Table 204-1 Minimum Densities for Design Loads from Materials (kN/m 3 ) 



' Material 

Density 

Material 

Density 


Aluminum 

Bituminous products 

Asphaltum 

Graphite 

Paraffin 

P. Petroleum, crude .... 
petroleum, refined 
petroleum, benzine 
Petroleum, gasoline 
; Pitch ... 

Tar 

i Brass 

Bronze 

Cast-stone masonry (cement, stone, sand) 

Cement, portland, loose 
Ceramic tile 

-Charcoal 

Cinder fill . 

Cinders, dry, in bulk 

Coal 

Anthracite, piled . 

Bituminous, piled 

Lignite, piled 

Peat, dry, piled 

Concrete, plain 

Cinder 

£\pandec!-slag aggregate 

Haydite, burned-clay aggregate 

Slag 

Stone 

If Vcrmiculite and perlite aggregate, non load-bearing 
Other light aggregate, load bearing 

Concrete, reinforced 
Cinder 
Slag .... 

Stone, including gravel 

Copper 

Cork, compressed 

Earth, not submerged 

}■" Clay, dry 

Clay, damp 
Clay and gravel, dry 
Silt, moist, loose .. 

Silt, moist, packed 

Jfpp. Silt, flowing 

Sand and gravel, dry, loose .. 

Sand and gravel, dry, packed . 

Sand and gravel, wet 

Earth, submerged 

Clay 

Soil 

River mud 

Sand or gravel 

||£ Sand or gravel and clay 

Glass 

Gravel, dry 

Gypsum, loose 
Gypsum, wallboard 
Ice 

gjjioh 

Cast 

HP;: Wrought 
Lead 


26.7 

12.7 

21.2 

8.8 

8.6 

7.9 
7.2 
6.6 

10.8 
11.8 

82.6 

86.7 

22.6 

14.1 

23.6 

1.9 

9.0 

7.1 

8.2 
7.4 
7.4 
3.6 


17.0 

15.7 

14.1 

20.7 

22.6 

....3. 9-7.9 
.11.0-16,5 

17.4 

21.7 
23.6 

87.3 

2.2 


9.9 

17.3 
15.7 

12.3 
15.1 

17.0 

15.7 
. 17.3 

18.9 

12.6 

11.0 

14.1 
9.4 

10.2 

25.1 

16.3 
. 11.0 
. 7.9 

. 9.0 

70.7 

75.4 

111.5 


Lime 

Hydrated, loose 

Hydrated, compacted 

Masonry, Ashlar Stone 

Granite 

Limestone, crystalline .... 

Limestone, oolitic 

Marble 
Sandstone 
Masonry, Brick 

Hard, low absorption 
Medium, medium absorption 
Soft, high absorption 

Masonry, Concrete (solid portion) 

Lightweight units 

Medium weight units 
Normal weight units 

Masonry grout 

Masonry, Rubble Stone 

Granite 

Limestone, crystalline 

Limestone, oolitic 

Marble 
Sandstone 

Mortar, cement or lime 


5.0 

7.1 


... 25.9 
... 25.9 
... 21.2 

27.2 

22.6 

20.4 
18.1 
15.7 

16.5 

19.6 

21.2 

22.0 

24.0 

23.1 

21.7 

24.5 

21.5 
20.4 


Particle board 7.1 

Plywood 5.7 

Riprap, not submerged 

Limestone 13.0 

Sandstone 14.1 

Sand 

Clean and dry 14.1 

River, dry 16.7 

Slag 

Bank 

Bank screenings 

Machine 

Sand 

Slate 

Steel, cold-drawn 

Stone, quarried, piled 

Basalt, granite, gneiss 
Limestone, marble, quartz 
Sandstone 

Shale 

Greenstone, hornblende 

Terracotta, architectural 

Voids filled 

Voids unfilled 

Tin 

Water 

Fresh 

Sea 


11.0 

17.0 

15.1 

8.2 

27.0 

77.3 

15.1 

14.9 

12.9 
14.5 
16.8 

18.9 
. 11.3 

72.1 

9.8 

10.1 


Wood (see Chapter 6 for relative densities for Philippine wood) 

Zinc, rolled sheet 70.5 


National Structural Code of the Philippines Volume 1, 7th Edition, 2015 



2-14 CHAPTER 2 - Minimum Design Loads 


Table 204-2 Minimum Design Dead Loads (kPa) 


Component 


Load Component 


Load Component 


Load 


FRAME WALLS 


CEILINGS 

Acoustical fiber board 0.05 

Gypsum board (per mm 

thickness) 0.008 

Mechanical duct allowance 0.20 

Plaster on tile or concrete 0.24 

Plaster on wood lath 0,38 

Suspended steel channel 

system 0.10 

Suspended metal lath and cement 

plaster 0.72 

Suspended metal lath and 

gypsum plaster 0.48 

Wood furring suspension 

system 0.12 

COVERINGS, Roof and Wall 

Asphalt shingles 0.10 

Cement tile 0.77 

Clay tile (for mortar add 0.48 kPa) 

Book tile, 50 mm 0.57 

Book tile, 75 mm 0.96 

Ludowici 0.48 

Roman * 0.57 

Spanish 0.91 

Composition: 

Three-ply ready roofing 0.05 

Four-ply felt and gravel 0.26 

Five-ply felt and gravel 0.29 

Copper or tin 0.05 

Corrugated asbestos-cement 

roofing 0,19 

Deck, metal 20 gage 0.12 

Deck, metal, 18 gage 0.14 

Fiberboard, 13mm 0.04 

Gypsum sheathing, 1 3 mm 0. 1 0 

Insulation, roof boards (per mm 
thickness) 

Cellular glass 0.0013 

Fibrous glass 0.0021 

Fiberboard 0.0028 

Perlite 0.0015 

Polystyrene foam 0.0004 

Urethane foam with skin ... 0.0009 
Plywood (per mm thickness) 0.0060 

Rigid insulation, 13 mm 0,04 

Skylight, metal frame, 

10mm wire glass 0.38 

Slate, 5 mm 0.34 

Slate, 6 mm 0.48 

Waterproofing membranes: 
Bituminous, gravel-covered . 0.26 
Bituminous, smooth surface .. 0.07 

Liquid, applied 0.05 

Single-ply, sheet 0.03 

Wood sheathing (per mm 

thickness) 0.0057 

Wood shingles 0.14 


FLOOR FILL 

Cinder concrete, per mm 0.017 

Lightweight concrete, per mm.. 0.0 15 

Sand, per mm 0.015 

Stone concrete, per mm 0.023 

FLOOR AND FLOOR FINISHES 

Asphalt block (50 mm), 13 mm 

mortar L44 

Cement finish (25 mm) on stone- 

concrete fill L53 

Ceramic or quarry tile (20 mm) 

on 13 mm mortar bed 0.77 

Ceramic or quarry tile (20 mm) 

on 25 mm mortar bed 1.10 

Concrete fill finish (per mm 

thickness) 0.023 

Hardwood flooring, 22 mm 0. 19 

Linoleum or asphalt tile, 6mm ....0.05 
Marble and mortar on stone- 

concrete fill L58 

Slate (per mm thickness) 0.028 

Solid flat tile on 25-mm mortar 

base * 1-10 

Subflooring, 1 9 mm 0. 1 4 

Terrazzo (38 mm) directly on 

slab 0.91 

Terrazzos (25 mm) on stone- 

concrete fill L53 

Terrazzo (25 mm) on 50-mm stone 

concrete L53 

Wood block (75 mm) on mastic, 

no fill 0.48 

Wood block (75 mm) on 13-mm 
mortar base 0.77 

FRAME PARTITIONS 

Movable partitions 0.24 

Movable partitions (steel) 0.19 

Wood or steel studs, 13 mm gypsum 

board each side 0.38 

Wood studs, 50 x 100, unplastered 

0.19 

Wood studs 50 x i 00, plastered one 

side 0.57 

Wood studs 50 x 100, plastered two 
side 0.96 


Exterior stud walls: 

50x100 @ 400mm, 15 mm 
gypsum, insulated, 10 mm 

siding 0.53 

50x150 @ 400mm, 15 mm 
gypsum, insulated, 10 mm 

siding 0.57 

Exterior stud wall with brick 

veneer 2.30 

Windows, glass, frame and 

sash 0.38 

Clay brick wythes: 

100 mm 1-87 

200 mm 3.74 

300 mm 5.51 

400 mm 7.48 


CONCRETE MASONRY UNITS 


Hollow Concrete Masonry Units 
Unplastered. Add 0.24 kPa for 
each face plastered 


Grout \ 

Wythe thickness (mm) 

Spacing 1 

100 

150 ! 

200 i 

16.5-kN/m 3 Density of Unit 1 

No grout 1 

1.05 

1.15 1 

1.48 

800 ! 

L40 

1.53 1 

2.01 

600 

1.50 

1.63 ! 

2.20 

400 

1.79 

1.92 

2.54 

Full 

2.50 

2.63 1 

3.59 

1 19.6-kN/m 3 Density of Unit I 

No grout 

1.24 

1.34 : 

1.72 

800 

1.59 

f" 1.72 

2,25 

600 

1.69 

I 1.87 

2.44 

400 

1.98 

! 2,11 

2.82 

Full 

2.69 

2.82 

3.88 

21.2-kN/m 3 

Density of Unit 


No grout 

1.39 

! 1.44 

1,87 

800 

^ 1.74 

! 1.82 

2.39 

600 

1.83 

1 1.96 

2.59 

400 

2.13 

| 2.2 

2.92 

Full 

2.84 

| 2.97 

| 3.97 




Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 ~ Minimum Design Loads 2-15 


SECnONJ^ 


2«5.i 


General 


shall be the maximum loads expected by the 
or occupancy but in no case shall be less than 
che loads required by this section. 


Critical Distribution of Live Loads 


are 


arranged to 


create 


— mw ua.* structural members 
: : JUfentinuity. members shall be designed using the loading 
■Motions, which would cause maximum shear and 
moments. This requirement may be satisfied in 
^^^ilordance with the provisions of Section 205.3.2 or 
^^^^15.4.2, where applicable. 


205.3 Floor Live Loads 


General 


l88Mlf ifoni-e shall be designed for the unit live loads as set forth 


|^pte| .Tah1i» 205-1 . These loads shall be taken as the minimum 
loads of horizontal projection to be used in the design 
^^feS thnilrlings for the occupancies listed, and loads at least 
shall be assumed for uses not listed in this section but 
Jliltijat creates or accommodates similar loadings. 


^^^here;it can be determined in designing floors that the 
actual live load will be greater than the value shown in 
^jp^pfable 205-1 , the actual live load shall be used in the design 
^^l£pf such buildings or portions thereof. Special provisions 
^^^shall be made for machine and apparatus loads. 


Distribution of Uniform Floor Loads 


1111205.3.2 

^|||lWhere uniform floor loads are involved, consideration may 
limited to foil dead load on all spans in combination with 
full live load on adjacent spans and alternate spans. 






205.3.3 Concentrated Loads 

Floors shall be designed to support safely the uniformly 
distributed live loads prescribed in this section or the 
concentrated load given in Table 205-1 whichever 
produces the greatest load effects. Unless otherwise 
specified the indicated concentration shall be assumed to 
be uniformly distributed over an area 750-mm square and 
shall be located so as to produce the maximum load effects 
in the structural member. 

Provision shall be made in areas where vehicles are used or 
stored for concentrated loads, L, consisting of two or more 
loads spaced 1.5m nominally on center without uniform 
live loads. Each load shall be 40 percent of the gross weight 
of the maximum size vehicle to be accommodated. Parking 
garages for the storage of private or pleasure- type motor 
vehicles with no repair or refueling shall have a floor 
system designed for a concentrated load of not less than 
9 kN acting on an area of 0.015 nr without uniform live 
loads. The condition of concentrated or uniform live load, 
combined in accordance with Section 203.3 or 203.4 as 
appropriate, producing the greatest stresses shall govern. 

205.3.4 Special Loads 

Provision shall be made for the special vertical and lateral 
loads as set forth in Table 205-2. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-1 6 CHAPTER 2 - Minimum Design Loads 


Table 205-1 Minimum Uniform and Concentrated Live Loads 
Use or Occupancy Uniform Load 1 


Category 

1 . Access floor systems 

2. Armories 


3. Theaters, 
assembly 
areas 3 and 
auditoriums 


4. Bowling alleys, poolrooms 

and similar recreational 
areas 

5. Catwalk for maintenance 
access 


6, Cornices and marquees 


7. Dining rooms and restaurants 


8. Exit facilities 5 


9* Parking Garages and Ramps 


10. Hospitals 


1 1 . Libraries 


12. Manufacturing 


Description 

Office use 

Computer use 


Fixed seats 
Movable seats 
Lobbies and platforms 
Stage areas 


General storage and/or repair 

Public parking and ramps 

Private (residential) or pleasure- 
type motor vehicle storage 


Wards and rooms 


Laboratories and operating rooms 


Corridors above ground floor 
Reading rooms 
Stack rooms 

Corridors above ground floor 
Light 
Heavy 

Building corridors above ground 
floor 


Uniform Load 1 
kPa 



Concentrated Load 

kN 

9.0 2 



CO 

O 6 

bo 

t-x 

i 

l 

CO 

— 7 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 















CHAPTER 2 - Minimum Design Loads 2-17 


Table 205-1 Minimum Uniform and Concentrated Live Loads ( continued) 


Use or Occupancy 

Uniform Load 1 

Concentrated Load 

Category 

Description 

kPa 

kN 

•• 

Call centers and business processing 
offices 

2.9 

9.0 

13, Office 

Lobbies and ground floor corridors 

4.8 

9.0 


Other offices 

2.4 

9.0- 

: 14. Printing plants 

Press rooms 

7.2 

11.0- 

Composing and linotype rooms 

4.8 

9.0 2 


Basic floor area 

1.9 

0 s 

. 15. Residential* 

Exterior balconies 

2.9 4 

0 

Decks 

1.9 4 

0 


Storage 

1.9 

0 

16. Restrooms 9 

-- 


-- 

1 1. Reviewing stands, 

grandstands, bleachers, and 
folding and telescoping seating 

- 

4.8 

0 

18. Roof decks 

Same as area served or occupancy 

-- 

-- 


Classrooms 

1.9 

4,5“ 

19. Schools 

Corridors above ground floor 

3.8 

4.5 

i nr 

Ground floor corridors 

4.8 

4.5 

20. Sidewalks and driveways 

Public access 

12.0 

__ 7 

21. Storage 

Light 

6.0 


Heavy 

12,0 

- 

22. Stores 

Retail 

4.8 

4.5 2 

Wholesale 

6.0 

13.4 2 

23. Pedestrian bridges and 
walkways 

- 

4.8 

-- 


Notes for Table 205- 1 

1 See Section 2 05. 5 for li ve load reductions. 

See Section 205.3.3 , first paragraph , for area of load 
application. 

' Assembly areas include such occupancies as dance halls , drill 
rooms, gymnasiums, playgrounds, plazas, terraces and similar 
occupancies that are generally accessible to the public. 

4 For special-purpose roofs, see Section 205. 4. 4. 

5 Exit facilities shall include such uses as corridors serving an 
occupant load of 10 or more persons, exterior exit balconies, 
stairways t fire escapes and similar uses. 


Individual stair treads shall be designed to support a 1.3 N 
concentrated load placed in a position that would cause 
maximum stress. Stair stringers may be designed for the 
uniform load set forth in the table. 

See Section 205.3.3, second paragraph , for concentrated 
loads . See Table 205-2 for vehicle barriers. 

Residential occupancies include private dwellings, apartments 
and hotel guest rooms. 

Restroom loads shall not be less than the load for the 
occupancy with which they are associated, but need not exceed 
2.4 kPa. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-18 CHAPTER 2 - Minimum Design Loads 


Table 205-2 Special Loads 1 


Use or Occupancy 

Vertical Load 

Lateral Load 

Category 

Description 

kPa 

kPa 

1 . Construction, public access at site (live 
load) 

Walkway 

7.2 


Canopy 

7.2 

- 

2. Grandstands, reviewing stands, 

bleachers, and folding and telescoping 
seating (live load) 

Seats and footboards 

1 .75 2 

See Note 3 

3, Stage accessories (live load) 

Catwalks 

1.9 

- 

Follow spot, projection 
and control rooms 

2.4 

- 

4, Ceiling framing (live load) 

Over stages 

1.0 

- 

All uses except over 
stages 

0.5 4 

- 

5. Partitions and interior walls, 

- 

- 

0.25 

6. Elevators and dumbwaiters (dead and 
live loads) 

- 

2*total load 

- 

7. Cranes (dead and live loads) 

Total load including 
impact increase 

1 .25*tota! load^ 

0.10*total load 6 

8. Balcony railings and guardrails 

Exit facilities serving an 
occupant load greater 
than 50 persons 

- 

0.75 kN/m 7 

Other than exit facilities 

- 

0.30 kN/m 7 

Components 

- 

1.2® 

9. Vehicle barriers 

- 

- 

27 kN ? 

10. Handrails 

- 

See Note 10 

See Note 10 

11. Storage racks 

Over 2.4 m high 

Total loads” 

See Table 208-13 

12. Fire sprinkler structural support 

- 

1.1 kN plus weight of 
water-filled pipe”’ 

See Table 208-13 


Notes for Table 205-2 

1 The tabulated loads are minimum loads. Where other vertical loads required by the design would cause greater stresses, they shall be used. Loads are in kPa unless 
otherwise indicated in the table. 


' Units is kN/m. 

i Lateral sway bracing loads of 3 50 N/m parallel and 145 N/m perpendicular to seat and footboards. 

4 Does not apply to ceilings that have sufficient access from below, such that access is not required within the space above the ceiling . Does not apply to ceilings if the attic 
areas above the ceiling are not provided with access. This live had need not be considered as acting simultaneously with other live loads imposed upon the ceiling framing 
or its supporting structure. 

•' The impact factors included are for cranes with steel wheels riding on steel rails. They may be modified if substantiating technical data acceptable to the building official 
is submitted Live loads on crane support girders and their connections shall be taken as the maximum crane wheel loads. For pendant-operated traveling crane support 
girders and their connections, the impact factors shall be i. /ft 

* This applies in the direction parallel to the runway rails (longitudinal). The factor for forces perpendicular to the rad is 0.20 * the transverse traveling loads (trolley, cab , 
books and lifted loads). Forces shall be applied at top of rail and may be distributed among rails of multiple rail cranes and shall he distributed with due regard for lateral 
stiffness of the structures supporting these rails. 

? A load per lineal meter (kN/m) to be applied horizontally at right angles to the top rail. 

tt Intermediate rails , panel fillers and their connections shall be capable of withstanding a load of 1. 2 kPa applied horizontally at right angles over the entire tributary area, 
including openings and spaces between rails. Reactions due to this loading need not be combined with those of Note 7. 

9 A horizontal load applied at right angles to the vehicle barrier at a height of 450 mm above the parking surface . The force may be distributed over a 300-mm square. 

t0 The mounting of handrails shall be such that the completed handrail and supporting structure are capable of withstanding a load of at least 890 N applied in any direction 
at any point on the rail. These loads shall not be assumed to act cumulatively with Note 9. 

Vertical members of storage racks shall be protected from impact forces of operating equipment, or racks shall be designed so that failure of one vertical mem be) will not 
came collapse of more than the bay or bays directly supported by that member. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-1 9 


/’ The / I~kN had is to be applied to any single fire sprinkler support point but not simultaneously to all support joints. 

205.4 Roof Live Loads 205.4.4 Special Roof Loads 


205.4.1 General 


Roofs shall be designed for the unit live loads, L r , set forth 
in Table 205-3. The live loads shall be assumed to act 
vertically upon the area projected on a horizontal plane. 

205.4.2 Distribution of Loads 

Where uniform roof loads are involved in the design of 
structural members arranged to create continuity, 
consideration may be limited to full dead loads on all spans 
in combination with full roof live loads on adjacent spans 
and on alternate spans. 

Exception: 

Alternate span loading need not be considered where the 
uniform roof live load is 1.0 kPa or more , 

For those conditions where light-gage metal preformed 
structural sheets serve as the support and finish of roofs, 
roof structural members arranged to create continuity shall 
be considered adequate if designed for full dead loads on 
all spans in combination with the most critical one of the 
following superimposed loads: 

|l| ; The uniform roof live load, L r , set forth in Table 205- 
IS 3 on all spans. 

2. A concentrated gravity load, L r , of 9 kN placed on any 
span supporting a tributary area greater than 1 8 nr to 
HI' create maximum stresses in the member, whenever 
H. this loading creates greater stresses than those caused 
by the uniform live load. The concentrated load shall 
be placed on the member over a length of 0.75 m along 
the span. The concentrated load need not be applied to 
more than one span simultaneously. 

§3* Water accumulation as prescribed in Section 206.7. 

205.4.3 Unbalanced Loading 

Unbalanced loads shall be used where such loading will 
result in larger members or connections. Trusses and 
arches shall be designed to resist the stresses caused by unit 
Jive loads on one-half of the span if such loading results in 
reverse stresses, or stresses greater in any portion than the 
stresses produced by the required unit live load on the 
entire span. For roofs whose structures are composed of a 
stressed shell, framed or solid, wherein stresses caused by 
any point loading are distributed throughout the area of the 
shell, the requirements for unbalanced unit live load design 
may be reduced 50 percent. 


Roofs to be used for special purposes shall be designed for 
appropriate loads as approved by the building official 
Greenhouse roof bars, purlins and rafters shall be designed 
to carry a 0.45 kN concentrated load, L r , in addition to the 
uniform live load 

205.5 Reduction of Live Loads 

The design live load determined using the unit live loads as 
set forth in Table 205-1 for floors and Table 205-3, Method 
2, for roofs may be reduced on any member supporting 
more than 15 nr, including flat slabs, except for floors in 
places of public assembly and for live loads greater than 
4.8 kPa, in accordance with the following equation: 

R = r(A ~~ 15 ) (205-1) 

The reduction shall not exceed 40 percent for members 
receiving load from one level only, 60 percent for other 
members or R , as determined by the following equation: 

R = 23 . 1(1 + D/L) (205-2) 

where 

A = area of floor or roof supported by the member, nr 
D - dead load per square meter of area supported by the 
member, kPa 

L = unit live load per square meter of area supported by 
the member, kPa 
R ~ reduction in percentage, 

r = rate of reduction equal to 0.08 for floors. See Table 
205-3 for roofs 

For storage loads exceeding 4.8 kPa, no reduction shall be 
made, except that design live loads on columns may be 
reduced 20 percent. 

The live load reduction shall not exceed 40 percent in 
garages for the storage of private pleasure cars having a 
capacity of not more than nine passengers per vehicle. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-20 CHAPTER 2 - Minimum Design Loads 

205*6 Alternate Floor Live Load Reduction 

As an alternate to Equation 205-1, the unit live loads set 
forth in Table 205-1 may be reduced in accordance with 
Equation 205-3 on any member, including flat slabs, 
having an influence area of 40 m 2 or more. 


L = L o 


0.25 + 4.57 


L 


/A, 


(205-3) 


where 


A, = influence area, nr 

L = reduced design live load per square meter of area 
supported by the member 


L 0 = unreduced design live load per square meter of area 
supported by the member (Table 205-1) 

The influence area A, is four times the tributary area for 
a column, two times the tributary area for a beam, equal to 
the panel area for a two-way slab, and equal to the product 
of the span and the full flange width for a precast T-beam. 

The reduced live load shall not be less than 50 percent of 
the unit live load L 0 for members receiving load from one 
level only, nor less than 40 percent of the unit live load L 0 
for other members. 



5. Greenhouses, lath houses 
agricultural buildings. 5 

1 For special-purpose roofs, see Section 205.4.4. 

2 See Sections W5 5 and 205.6 for live-load reductions. The rate of reduction r in Equation 
if, fall" The Lin, um reduction, II. shall no, exceed the value indicated m the table. 

1 A flat roof is any roof with a slope less than 1 .unit vertical in 48-unit horizontal 1 2 % slope), 
is in addition to the ponding load required by Section 206. 7. 

4 See definition in Section 202 . 

5 See Section 205.4.4 for concentrated load requirements for greenhouse roof members. 


205-1 shall be as indicated 
The live load for flat roofs 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-21 



loads;; 

20 6.1 General 


In addition to the other design loads specified in this 
chapter, structures shall be designed to resist the loads 
specified in this section and the special loads set forth in 
Table 205-2. See Section 207 for design wind loads and 
Section 208 for design earthquake loads. 

206.2 Other Loads 

Buildings and other structures and portions thereof shall be 
designed to resist all loads due to applicable fluid 
pressures, f\ lateral soil pressures, H , ponding loads, P, 
and self-straining forces, 7\ See Section 206.7 for ponding 
loads for roofs. 

206.3 Impact Loads 

The live loads specified in Sections 205.3 shall be assumed 
to include allowance for ordinary impact conditions. 
Provisions shall be made in the structural design for uses 
and loads that involve unusual vibration and impact forces. 
See Section 206.9.3 for impact loads for cranes, and 
Section 206, 10 for heliport and helistop landing areas. 

206.3.1 Elevators 

All elevator loads shall be increased by 100% for impact 

206.3.2 Machinery 

For the purpose of design, the weight of machinery and 
moving loads shall be increased as follows to allow for 
impact: 

1 . Elevator machinery 1 00% 

2. Light machinery, shaft- or motor-driven 20% 

3. Reciprocating machinery or power-driven units 50% 

4. Hangers for floors and balconies 33% 

All percentages shall be increased where specified by the 
manufacturer. 


206.4 Anchorage of Concrete and Masonry Walls 

Concrete and masonry walls shall be anchored as required 
by Section 104.3.3. Such anchorage shall be capable of 
resisting the load combinations of Section 203.3 or 203.4 
using the greater of the wind or earthquake loads required 
by this chapter or a minimum horizontal force of 4 kN/m 
of wall, substituted for E. 

206.5 Interior Wall Loads 

Interior walls, permanent partitions and temporary 
partitions that exceed 1.8 m in height shall be designed to 
resist all loads to which they are subjected but not less than 
a load, L, of 0.25 kPa applied perpendicular to the walls. 
The 0.25 kPa load need not be applied simultaneously with 
wind or seismic loads. The deflection of such walls under 
a load of 0.25 kPa shall not exceed 1/240 of the span for 
walls with brittle finishes and 1/120 of the span for walls 
with flexible finishes. See Table 208-13 for earthquake 
design requirements where such requirements are more 
restrictive. 


Exception: 


Flexible, folding or portable partitions are not required to 
meet the load and deflection criteria but must be anchored 
to the supporting structure to meet the provisions of this 
code . 

206.6 Retaining Walls 

Retaining walls shall be designed to resist loads due to the 
lateral pressure of retained material in accordance with 
accepted engineering practice. Walls retaining drained soil, 
where the surface of the retained soil is level, shall be 
designed for a load, H, equivalent to that exerted by a fluid 
weighing not less than 4.7 kPa per meter of depth and 
having a depth equal to that of the retained soil. Any 
surcharge shall be in addition to the equivalent fluid 
pressure. 

Retaining walls shall be designed to resist sliding by at 
least 1 .5 times the lateral force and overturning by at least 
1.5 times the overturning moment, using allowable stress 
design loads. 

206.7 Water Accumulation 

All roofs shall be designed with sufficient slope or camber 
to ensure adequate drainage after the long-term deflection 
from dead load or shall be designed to resist ponding load, 
P, combined in accordance with Section 203.3 or 203.4. 
Ponding load shall include water accumulation from any 
source due to deflection. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-22 CHAPTER 2 - Minimum Design Loads 


206.8 Uplift on Floors and Foundations 

In the design of basement floors and similar approximately 
horizontal elements below grade, the upward pressure of 
water, where applicable, shall be taken as the full 
hydrostatic pressure applied over the entire area. The 
hydrostatic load shall be measured from the underside of 
the construction. Any other upward loads shall be included 
in the design. 

Where expansive soils are present under foundations or 
slabs-on-ground, the foundations, slabs, and other 
components shall be designed to tolerate the movement or 
resist the upward loads caused by the expansive soils, or 
the expansive soil shall be removed or stabilized around 
and beneath the structure. 

206.9 Crane Loads 

206.9.1 General 

The crane load shall be the rated capacity of the crane. 
Design loads for the runway beams, including connections 
and support brackets of moving bridge cranes and monorail 
cranes shall include the maximum wheel loads of the crane 
and the vertical impact, lateral, and longitudinal forces 
induced by the moving crane. 

206.9.2 Maximum Wheel Load 

The maximum wheel loads shall be the wheel loads 
produced by the weight of the bridge, as applicable, plus 
the sum of the rated capacity and the weight of the trolley 
with the trolley positioned on its runway where the 
resulting load effect is maximum. 

206.9.3 Vertical Impact Force 

The maximum wheel loads of the crane shall be increased 
by the percentages shown below to determine the induced 
vertical impact or vibration force: 


Monorail cranes (powered) 

25% 

Cab-operated or remotely operated bridge 


cranes (powered) 

25% 

Pendant-operated bridge cranes (powered) 

10% 

Bridge cranes or monorail cranes with 


hand-geared ridge, trolley and hoist 

0% 




206.9.4 Lateral Force 

The lateral force on crane runway beams with electrically jj 
powered trolleys shall be calculated as 20% of the sum of 
the rated capacity of the crane and the weight of the hoist 
and trolley. The lateral force shall be assumed to act 
horizontally at the traction surface of a runway beam, in 
either direction perpendicular to the beam, and shall be |j 
distributed with due regard to the lateral stiffness of the 
runway beam and supporting structure. 




i M 
: 


206.9.5 Longitudinal Forces 

The longitudinal force on crane runway beams, except fori 
bridge cranes with hand-geared bridges, shall be calculated 
as 10% of the maximum wheel loads of the crane. The 
longitudinal force shall be assumed to act horizontally at 
the traction surface of a runway beam, in either direction 
parallel to the beam. 

206.10 Heliport and Helistop Landing Areas 

In addition to other design requirements of this chapter^ 
heliport and helistop landing or touchdown areas shall be : 
designed for the following loads, combined in accordance 
with Section 203.3 or 203.4: 

0 

1 . Dead load plus actual weight of the helicopter. 

2. Dead load plus a single concentrated impact load, Ljl 
covering 0. 1 0 nr of 0.75 times the fully loaded weight 
of the helicopter if it is equipped with hydraulic-type 
shock absorbers, or 1.5 times the fully loaded weighty 
of the helicopter if it is equipped with a rigid or skid' 
type landing gear. 

The dead load plus a uniform live load, L, of 4.8 kPa. The 
required live load may be reduced in accordance with 
Section 205.5 or 205.6. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-23 



^Buildings and other vertical structures shall be designed 
and constructed to resist wind loads as specified and 
presented in Sections 207A through 207F. 

0 Antenna towers and antenna supporting structures shall be 
; designed and constructed to resist wind loads as specified 
'and presented in ANSI/TIA-222-G-2005, entitled as 
“Structural Standards for Steel Antenna Towers and 
Antenna Supporting Structures and ANSI/TIA-222-G-1- 
2007, entitled as 44 Structural Standards for Steel Antenna 
Towers and Antenna Supporting Structures - Addendum L 

§207A General Requirements 






in this 

code have been significantly revised from NSCP 2001 and 
NSCP 2010 editions: The goal was to improve the 
Organization, clarity, and use of the wind load provisions 
by creating individual sub-sections organized according to 
applicable major subject areas: The wind load 
provisions are now presented in Sections 207 A through 
207F as opposed to prior editions ; where the provisions 
were contained in a single section. 


Sec turn 207 A provides the basic wind design 
parameters that are applicable to the various wind 


2078 through 207F . Items covered in Section 207 A 
include definitions, basic wind speed, exposure 
categories, internal ■ pressures, Cw enclosure 
classification, gust-effects, and topographic factors, 
among others! A general description of each section is 
provided below: C 

a Section 207 B discusses about Directional Procedure 
for Enclosed, Partially Enclosed, and Open Buildings 
of All Heights: The procedure is the former “ buildings 
of all heights method ” in NSCP 2010 (ASCE 7-05), 
Method 2 A simplified procedure, based on the 
Directional Procedure, is provided for buildings up to 
48m in heigltUrA\g :v/v. : :vev;w 

3 Section 207C discusses about Envelope Procedure for 

Enclosed and Partially Enclosed Low-Rise Buildings: 
This procedure is the former “low-rise buildings 
method" in NSCP 2010 (ASCE 7-05) Method 2. This 
section also incorporates NSCP 2010 (ASCE 7-05) 
Method I for MWFRS applicable to the MWFRS of 


enclosed simple diaphragm buildings less than 18 m 
in height . 

a Section 207 D discusses Other Structures and Building 

Appurtenances: A single section is dedicated to 
determining wind loads on non-building structures 
such as signs, rooftop structures, and towers, wA 

“ Section 207 E discusses about Components and 
Cladding . This code addresses the determination of 
component and cladding loads in a single section 
Analytical and simplified methods are provided based 
on the building height. Provisions for open buildings 
and building appurtenances are also addressed. 

a Section 207 F discusses about Wind Tunnel Procedure . 

207A.1 Procedures 
207A.1.1 Scope 

Buildings and other structures, including the Main Wind- 
Force Resisting System (MWFRS) and all components and 
cladding (C&C) thereof, shall be designed and constructed 
to resist the wind loads determined in accordance with 
Section 207A through 207F. The provisions of this section 
define basic wind parameters for use with other provisions 
contained in this code. 


Commentary: 

The procedures specified in this code provide wind 
pressures and forces for the design of MWFRS and for the 
design of components and cladding (C&C) of buildings 
and other structures. The procedures involve the 
determination of wind directionality and velocity pressure, 
the selection or determination of an appropriate gust effect 
factor, and the selection of appropriate pressure or force 
coefficients. The procedure allows for the level of 
structural reliability required, the effects of differing wind 
exposures, the speed-up effects of certain topographic 
features such as hills and escarpments, and the size and 
geometiy of the building or other structure under 
consideration. The procedure differentiates between rigid 
and flexible biuldings and other structures, and the results 
generally envelop the most critical load conditions for the 
design of MWFRS as well as C&C. 

The pressure and force coefficients provided in Sections 
207B , 207 C, 207 D, and 207E have been assembled from 
the latest boundary-layer wind-tunnel and full-scale tests 
and from previously available literature. Because the 
boundary-layer wind-tunnel results were obtained for 
specific types of building, such as low - or high-rise 
buildings and buildings having specific types of structural 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-24 CHAPTER 2 - Minimum Design Loads 


framing systems, the designer is cautioned against 
indiscriminate interchange of values among the figures 
and tables. 

207A.1.2 Permitted Procedures 

The design wind loads for buildings and other structures, 
including the MWFRS and C&C elements thereof, shall be 
determined using one of the procedures as specified in this 
article. An outline of the overall process for the 
determination of the wind loads, including section 
references, is provided in Figure 207A.1-L 


Commentary: 

The design wind loads for buildings and other 
structures , including the MWFRS and C&C elements 
thereof shall be determined using one of the procedures 
as specified in this article . An outline of the overall 
process for the determination of the wind loads, 
including section references, is provided in Figure 
207 A. 1-1. 

This version of the wind load standard provides several 
procedures (as illustrated in Table 207 A. 1-1) from 
which the designer can choose. 

For MWFRS: 

1. Directional Procedure for Buildings of All Heights 
(Section 207B) 

2. Envelope Procedure for Low-Rise Buildings 
(Section 207C) 

3. Directional Procedure for Building Appurtenances 
and Other Structures (Section 207D) 

4. Wind Tunnel Procedure for All Buildings and Other 
Structures (Section 207 F) 

For Components and Cladding: 

1. Analytical Procedure for Buildings and Building 
Appurtenances (Section 207E) 

2. Wind Tunnel Procedure for All Buildings and Other 
Structures (Section 207 F) 

A M simplified method’* for which the designer can select 
wind pressures directly from a table without any 
calculation ; when the building meets all the 
requirements for application of the method, is provided 
for designing buildings using the Directional Procedure 
(Section 207 B, Part 2), the Envelope Procedure (Section 


207C, Part 2) and the Analytical Procedure jorffi 
Components and Cladding (Section 207E). 

Limitations . The provisions given under Section || 
207 A. 1.2 apply to the majority of site locations and 
buildings and structures , but for some projects, these 
provisions may be inadequate. Examples of site H 
locations and buildings and structures (or portions f 
thereof) that may require other approved standards, f 
special studies using applicable recognized literature f 
pertaining to wind effects , or using the wind tunnel |g 
procedure of Section 207 F include: 

1. Site locations that have channeling effects or wakes 
from upwind obstructions. Channeling effects cant, 
be caused by topographic features (e.g., a mountain § 
gorge) or buildings (e.g., a neighboring tall 
building or a cluster of tall buildings). Wakes cant |' 
be caused by hills or by buildings or other f 
structures. S 


2. Buildings with unusual or irregular geometric 
shape, including barrel vaults, and other buildings 
whose shape (in plan or vertical cross-section) 
differs significantly from the shapes in Figures % 
207B.4-1, 207 B. 4-2, 207 B. 4-7, 207 C. 4-1, anc§ : 
207E.4-1 to 207E.4-7. Unusual or irregular f 
geometric shapes include buildings with multiple | 
setbacks, curved facades, or irregular plansi 
resulting from significant indentations org 
projections, openings through the building, org 
multi-tower buildings connected by bridges. 


3. Buildings with response characteristics that result 
in substantial vortex-induced and/or torsional 
dynamic effects, or dynamic effects resulting from I 
aero-elastic instabilities such as flutter or | 
galloping. Such dynamic effects are difficult to') 
anticipate, being dependent on many factors, but) 
should be considered when any one or more of the 
following apply: 


i. 

ii. 


in. 


iv. 


The height of the building is over 120 m. ]\ 

The height of the building is greater than 4 
times its minimum effective width B min . as 
defined below. 1 

The lowest natural frequency of the building 
is less than n t = 0.25 Hz. 

The reduced velocity 


niBv 


>5 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-25 


:Wiere-\: 

-f,- z “ 0 . 6 h 

V z " the mean hourly velocity at height z 

The minimum effective width B min is defined as the 
minimum value of £ hiBfY, h t considering all wind 
directions . The summations are performed over the 
|| %eight of the building for each wind direction, h it is the 
height above grade of level /, and B L is the width at level 
' i normal to the wind direction. 

4 \ Bridges, cranes , electrical transmission lines, 
guyed masts , highway signs and lighting structures , 
telecommunication towers, and flagpoles. 

:[ When undertaking detailed studies of the dynamic 
response to wind forces, the fundamental frequencies of 
: f$he structure in each direction under consideration 
should be established using the structural properties 
ami deformational characteristics of the resisting 
, elements in a properly substantiated analysis, and not 
utilizing approximate equations based on height f 

Shielding * Due to the lack of reliable analytical 
% procedures for predicting the effects of shielding 
f provided by buildings and other structures or by 
f topographic features, reductions in velocity pressure 
%fhte to shielding are not permitted under the provisions 
fpf this chapter. However, this does not preclude the 
i determination of shielding effects and the corresponding 
Inductions in velocity pressure by means of the wind 
fhmnel procedure in Section 207F . 

207AJ.2.1 Main Wind-Force Resisting System 
(MWFRS) 

V\ tnd loads for MWFRS shall be determined using one of 
||Iie fallowing procedures: 

1. Directional Procedure for buildings of all heights as 
specified in Section 207B for buildings meeting the 
requirements specified therein; 

2. Envelope Procedure for low-rise buildings as specified 
in Section 207C for buildings meeting the 
requirements specified therein; 

3* Directional Procedure for Building Appurtenances 
(rooftop structures and rooftop equipment) and Other 
Structures (such as solid freestanding walls and solid 
j| :/ freestanding signs, chimneys, tanks, open signs, lattice 
frameworks, and trussed towers) as specified in 
Section207D; or 


4. Wind Tunnel Procedure for all buildings and all other 
structures as specified in Section 207F. 

207A.L2.2 Components and Cladding 

Wind loads on components and cladding on all buildings 
and other structures shall be designed using one of the 
following procedures: 

1 . Analytical Procedures provided in Parts 1 through 6, 
as appropriate, of Section 207E; or 

2. Wind Tunnel Procedure as specified in Section 207F. 

207A.2 Definitions 

The following definitions apply to the provisions of 
Section 207: 

APPROVED is an acceptable to the authority having 
jurisdiction. 

BASIC WIND SPEED, V is a three-second gust speed at 
10m above the ground in Exposure C (see Section 
207A.7.3) as determined in accordance with Section 
207A.5.1. 

BUILDING, ENCLOSED is a building that does not 
comply with the requirements for open or partially 
enclosed buildings. 

BUILDING ENVELOPE is a cladding, roofing, exterior 
walls, glazing, door assemblies, window assemblies, 
skylight assemblies, and other components enclosing the 
building. 

BUILDING AND OTHER STRUCTURE, FLEXIBLE 
are slender buildings and other structures that have a 
fundamental natural frequency less than 1 Hz. 

BUILDING, LOW-RISE are enclosed or partially 
enclosed buildings that comply with the following 
conditions: 

1 . Mean roof height h less than or equal to 1 8m. 

2. Mean roof height h does not exceed least horizontal 
dimension. 

BUILDING, OPEN is a building having each wall at least 
80 percent open. This condition is expressed for each wall 
by the equation A 0 > 0. 8A g . 


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2-26 CHAPTER 2 - Minimum Design Loads 


A g = the gross area of that wail in which A 0 is 
identified, in m 2 


A 0 = total area of openings in a wall that receives 
positive external pressure, in m 2 



Figure 207 A. 1-1 

Outline of Process for Determining Wind Loads. Additional Outlines and User Notes are Provided at the Beginning of each 
Chapter for more Detailed Step-By-Step Procedures for Determining the Wind Loads 

These conditions are expressed by the following equations: 

1. A a > 1. 10A„i 

2. A 0 > 0.37 m 2 or 0.0L4 g , whichever is smaller, and 
A oi /A si < 0.20 

where: 

A 0 ,Ag = are as defined for Open Building 
A oi = the sum of the areas of openings in the 
building envelope (walls and roof) not 
including A 0 , in m 2 

A si = the sum of the gross surface areas of the 
building envelope (walls and roof) not 
including A g , in m 2 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


BUILDING, PARTIALLY ENCLOSED is a building 
that complies with both of the following conditions: 

1. The total area of openings in a wall that receives 
positive external pressure exceeds the sum of the areas 
of openings in the balance of the building envelope 
(walls and roof) by more than 10 percent. 

2. The total area of openings in a wall that receives 
positive external pressure exceeds 0.37 nr. 

or 1 percent of the area of that wall, whichever is smaller, 
and the percentage of openings in the balance of the 
building envelope does not exceed 20 percent. 








Components can be part of the MWFRS when they act as 
or roof diaphragms, but they may also be 
individual components. The engineer needs to 
^^Ullpriate loadings for design of components, which 
certain components to be designed for more 
llhfeohe type of loading, for example, long-span roof 
p^^^P||||Id^ be designed for loads associated with 
'MWFRS* and individual members of trusses should also be 
^ils%h ; ed for component and cladding loads ( Mehta and 
Examples of cladding include wall 
curtain walls, roof coverings, exterior windows 
operable) and doors, and overhead doors. 


ft ^^PHRAGM in wind load applications has been added 
7-10. This definition, for the case of untopped 


^^gdecks, differs somewhat from the definition used in 
of ASCE 7-10 because diaphragms under 
^^J^Bads':are expected to remain essentially elastic. 


WIND AREA, A is an effective wind area 
^|||h| area of the building surface used to determine ( GC p ). 
^^p||%eadoes not necessarily correspond to the area of the 
^^^ffinf-surface contributing to the force being considered. 


cases arise. In the usual case, the effective wind area 
correspond to the area tributary to the force 
^fc^fipbnent being considered. For example, for a cladding 




the effective wind area may be equal to the total area 
h6 panel; For a cladding fastener, the effective wind 
the area of cladding secured by a single fastener. A 
^H^^liidnimay receive wind from several cladding panels. In 
^^tcase, the effective wind area is the area associated with 
P^|^^t|i<ddbad that is transferred to the mullion. 




^^^^^||cond case arises where components such as roofing 
wall studs, or roof trusses are spaced closely 
The area served by the component may become 
anc * narrow - To better approximate the actual load 
distribution in such cases, the width of the effective wind 
|0g|^uscd t0 eva ^ uate (fiCp) need not be taken as less than 
”^^^^|| : hird the length of the area. This increase in effective 
y y- Wind area has the effect of reducing the average wind 
pressure acting on the component. Note, however, that this 
e wind area should only be used in determining the 
^^CC p ) in Figures 207E.4-1 through 207E.4-6 and 207E.4- 
^^^||||||edndiiced wind load should be applied over the actual 
tributary to the component being considered. 

^^^^imembrane roof systems, the effective wind area is the 
, ■ : aiea of an insulation board (or deck panel if insulation is 
|/|pTft ot use d) if the boards are fully adhered (or the membrane 
|l a bhered directly to the deck). If the insulation boards or 
^^|!|||mbrane are mechanically attached or partially adhered, 
e — c ^ ve w * n ^ area Is the area of the board or membrane 
secured by a single fastener or individual spot or row of 
fjiflg adhesive. 


CHAPTER 2 - Minimum Design Loads 2-29 


For typical door and window systems supported on three 
or more sides, the effective wind area is the area of the door 
or window under consideration. For simple spanning doors 
(e.g., horizontal spanning section doors or coiling doors), 
large specialty constructed doors (e.g., aircraft hangar 
doors), and specialty constructed glazing systems, the 
effective wind area of each structural component 
composing the door or window system should be used in 
calculating the design wind pressure. 

MAIN WIND-FORCE RESISTING SYSTEM 
(MWFRS) can consist of a structural frame or an 
assemblage of structural elements that work together to 
transfer wind loads acting on the entire structure to the 
ground. Structural elements such as cross-bracing, shear 
walls, roof trusses, and roof diaphragms are part of the 
Main Wind-Force Resisting System (MWFRS) when they 
assist in transferring overall loads (Mehta and Marshall 
1998). 

WIND-BORNE DEBRIS REGIONS are defined to alert 
the designer to areas requiring consideration of missile 
impact design. These areas are located within tropical 
cyclone prone regions where there is a high risk of glazing 
failure due to the impact of wind-borne debris. 

207A.3 Symbols and Notations 

The following symbols and notation apply only to the 
provisions of Section 207A through 207F: 

A = effective wind area, in m 2 

Af - area of open buildings and other 

structures either normal to the wind 
direction or projected on a plane 
normal to the wind direction, in m 2 

A s = the gross area of that wall in which A 0 
is identified, in m 2 

Agi = the sum of the gross surface areas of 
the building envelope (walls and roof) 
not including A g , in m 2 

A 0 - total area of openings in a wall that 
receives positive external pressure, in 
m 2 

A oi = the sum of the areas of openings in the 
building envelope (walls and roof) not 
including A 07 in m 2 

A og ~ total area of openings in the building 
envelope in m 2 

A s = gross area of the solid freestanding 
wall or solid sign, in m 2 

a = width of pressure coefficient zone, in 
m 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-30 CHAPTER 2 - Minimum Design Loads 


B 

b 

b 

Cf 

C N 

Cp 

c 

D 

D' 

F 

G 

Gf 

(GC r ) 

(GC P ) 

i GC Pf) 

(GCpt) 

(GC pn ) 
Sq 
g R 

%v 

H 


- horizontal dimension of building 
measured normal to wind direction, in 
m 

- mean hourly wind speed factor in 
Equation 207A.9-16 from Table 
207A.9-1 

= 3-s gust speed factor from Table 

207A.9-1 

= force coefficient to be used in 
determination of wind loads for other 
structures 

= net pressure coefficient to be used in 
determination of wind loads for open 
buildings 

= external pressure coefficient to be 
used in determination of wind loads 
for buildings 

= turbulence intensity factor in 
Equation 207A.9-7 from Table 
207A.9-1 

- diameter of a circular structure or 
member, in m 

- depth of protruding elements such as 
ribs and spoilers, in m 

- design wind force for other structures, 
in N 

= gust-effect factor 

= gust-effect factor for MWFRS of 
flexible buildings and other structures 

- product of external pressure 
coefficient and gust-effect factor to be 
used in determination of wind loads 
for rooftop structures 

= product of external pressure 
coefficient and gust-effect factor to be 
used in determination of wind loads 
for buildings 

- product of the equivalent external 
pressure coefficient and gust-effect 
factor to be used in determination of 
wind loads for MWFRS of low-rise 
buildings 

- product of internal pressure 
coefficient and gust-effect factor to be 
used in determination of wind loads 
for buildings 

= combined net pressure coefficient for 
a parapet 

= peak factor for background response 
in Equations 207A.9-6 and 207 A. 9-1 0 

= peak factor for resonant response in 
Equation 207A.9-10 

= peak factor for wind response in 
Equations 207A.9-6 and 207A.9-10 

- height of hill or escarpment in 
Figure 207A.8-1, in m 


h = mean roof height of a building or 
height of other structure, except that 
eave height shall be used for roof |jj 
angle 6 less than or equal to 10°, in m 

h e = roof eave height at a particular wail, or 1 

the average height if the eave varies 
along the wall 

h p = height to top of parapet in Figure 
207B.6-4 and 207E.7-1 

I z ~ intensity of turbulence from 

Equation 207A.9-7 

K 1 ,K 2 ,I <3 “ multipliers in Figure 207A.8-1 to 
obtain K zt 

K d = wind directionality factor in | 

Table 207A.6-1 

K h = velocity pressure exposure coefficient 
evaluated at height z = h 

K 2 - velocity pressure exposure coefficient 
evaluated at height z 

K zt “ topographic factor as defined in 

Section 207A.8 j 

L - horizontal dimension of a building 

measured parallel to the wind 
direction, in m 

L h = distance upwind of crest of hill or |jj 
escarpment in Figure 207A.8-1 to . J 
where the difference in ground |j 

elevation is half the height of the hill 
or escarpment, in m 

L r = horizontal dimension of return comer | 
for a solid freestanding wall or solid 
sign from Figure 207D.4-1, in m 

L 7 ~ integral length scale of turbulence, in 


PnetlO 


integral length scale factor from | 
Table 207A.9-l,m 

reduced frequency from | 

Equation 207A.9-14 

approximate lower bound natural ^ 
frequency (Hz) from Section 
207A.9.2 

fundamental natural frequency, Hz 1 
design pressure to be used iri|jj| 
determination of wind loads for 
buildings, in N/m 2 

wind pressure acting on leeward & ce jM 

in Figure 207B.4-8, in N/m 2 

net design wind pressure from | 

Equation 207E.5-1, in N/m 2 

net design wind pressure for Exposure j 

B at h = 10 m and / = 1.0 from 

Figure 207E.5-1, in N/m 2 

combined net pressure on a parapet 

from Equation 207B.4-5, in N/m 2 

net design wind pressure front 

Equation 207C.6-1, in N/m 2 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-31 



simplified design wind pressure for 
Exposure B at h — 10 m and 
/ s= 1.0 from Figure 207C.6-1, in 
N/nf 

wind pressure acting on windward 
face in Figure 207B.4-8, in N/m 2 
background response factor from 
Equation 207A.9-8 
velocity pressure, in N/m 2 
velocity pressure evaluated at height 
z = ft, in N/m 2 

velocity pressure for internal pressure 
determination, in N/m 2 
velocity pressure at top of parapet, in 
N/nr 

velocity pressure evaluated at height z 
above ground, in N/m 2 
resonant response factor from 
Equation 207A.9-12 
values from Equations 207A.9-15 
reduction factor from 

Equation 207A.1 1-1 
value from Equation 207A.9-13 
vertical dimension of the solid 
freestanding wall or solid sign from 
Figure 207D.4-1, in m 
rise-to-span ratio for arched roofs 
height-to-width ratio for solid sign 
basic wind speed obtained from 
Figure 207A.5-1A through 207 A. 5- 
1C, in m/s. The basic wind speed 
corresponds to a 3-s gust speed at 10 
m above the ground in Exposure 
Category C 

unpartitioned internal volume, m 3 
mean hourly wind speed at height z 
m/s 

width of building in Figures 207E.4-3 
and 207E.4-5A and 207E.4-5B and 
width of span in Figures 207E.4-4 and 
207E.4-6, in m 

distance upwind or downwind of crest 
in Figure 207A.8-1, in m 
height above ground level, in m 
equivalent height of structure, in m 
nominal height of the atmospheric 
boundary layer used in this code. 
Values appear in Table 207A.9-1 
exposure constant from Table 
207A.9-1 


P 

€ 


€ 


X 

n 

e 


- damping ratio, percent critical for 

buildings or other structures 
= ratio of solid area to gross area for 
solid freestanding wall, solid sign, 
open sign, face of a trussed tower, or 
lattice structure 

= integral length scale power law 
exponent in Equation 2 07 A. 9-9 from 
Table 207A.9-1 

= adjustment factor for building height 
and exposure from Figures. 207C.6-1 
and 207 E. 5-1 

= value used in Equation 207A.9-15 
(see Section 207A.9.4) 

= angle of plane of roof from horizontal, 
in degrees 


207A.4 General 
207A.4.1 Sign Convention 

Positive pressure acts toward the surface and negative 
pressure acts away from the surface. 

207AA2 Critical Load Condition 

Values of external and internal pressures shall be combined 
algebraically to determine the most critical load. 

207AA3 Wind Pressures Acting on Opposite Faces of 
Each Building Surface 

In the calculation of design wind loads for the M WFRS and 
for components and cladding for buildings, the algebraic 
sum of the pressures acting on opposite faces of each 
building surface shall be taken into account. 

Commentary: 

Section 207A.4.3 is included in the code to ensure that 
internal and external pressures acting on a building 
surface are taken into account by determining a net 
pressure from the algebraic sum of those pressures . For 
additional information on the application of the net 
components and cladding wind pressure acting across a 
multilayered building envelope system, including 
air-permeable cladding , refer to Section C207E . 1.5. 


3-s gust-speed power law exponent 
from Table 207A.9-1 
reciprocal of a from Table 207A.9-1 
mean hourly wind-speed power law 
exponent in Equation 207A.9-16 from 
Table 207A.9-1 

National Structural Code of the Philippines Volume I, 7th Edition, 2015 


i 


2-32 CHAPTER 2 - Minimum Design Loads 


207A.5 Wind Hazard Map 
207A.5.1 Basic Wind Speed 

The basic wind speed, V, used in the determination of 
design wind loads on buildings and other structures shall 
be determined from Figure 207A.5-1 as follows, except as 
provided in Section 207A.5.2 and 207 A. 5.3: 

For Occupancy Category III, IV and V buildings and other 
structures - use Figure 207A.5-1 A. 

For Occupancy Category 11 buildings and other structures 

- use Figure 207A.5-1.B. 

For Occupancy Category I buildings and other structures 

- use Figure 207A.5-1C. 

The wind shall be assumed to come from any horizontal 
direction. The basic wind speed shall be increased where 
records or experience indicate that the wind speeds are 
higher than those reflected in Figure 207A.5-1 . 

Commentary: 

This edition of NSCP departs from prior editions by 
providing wind maps that are directly applicable for 
determining pressures for strength design approaches . 
Rather than using a single map with importance factors 
and a load factor for each building occupancy category, 
in this edition there are different maps for different 
categories of building occupancies . The updated maps 
are based on a new and more complete analysis of 
tropical cyclone characteristics (Vickery et al 2008a, 
2008b and 2009) performed over the past 10 years. 

The decision to move to multiple-strength design maps 
in conjunction with a wind load factor of LO instead of 
using a single map used with an importance and a load 
factor of 1.6 relied on several factors important to an 
accurate wind specification : 

1. A strength design wind speed map brings the wind 
loading approach in line with that used for seismic 
loads in that they both essentially eliminate the use 

of a load factor for strength design. 


2. Multiple maps remove inconsistencies in the use of 
importance factors that actually should vary with ?|f 
location and between tropical cyclone-prone and 
non-tropical cyclone-prone regions for Occupcmcyf) 
Category ill, IV and V structures and acknowledge^ 
that the demarcation between tropical cyclone anclfj 
non-tropical cyclone winds change with the 
recurrence interval. 


3 . 


4. 


The new maps establish uniformity in the return 
period for the design-basis winds , and they more j 
clearly convey that information. 




The new maps, by providing the design wind speed 
directly , more clearly inform owners and their : || 
consultants about the storm intensities for which y 
designs are performed. 


Selection of Return Periods, in the development oftheyy 
design wind speed map used in Section 207 NSCP 2010, yy 
the Wind Load Subcommittee evaluated the wind'f 
importance factor , I w , that had been in use since 1982.% 
The task committee recognized that using a uniform 
value of the wind importance factor probably was not 
appropriate because risk varies with location along the y 
coast. 


To determine the return periods to be used in the newj 
mapping approach, the task committee needed to meet y 
with PAG AS A scientists, gather historical records and 
evaluate representative return periods for wind speeds | 
determined in accordance with Section 207 NSCP 2010 
and earlier, wherein determination of pressures \ 
appropriate for strength design started with mapped 
wind speeds, but involved multiplication by importance's 
factors and a wind load factor to achieve pressures that | 
were appropriate for strength design. Furthermore , it - 
was assumed that the variability of the wind speed 
dominates the calculation of the wind toad factor. The 
strength design wind load, W T . is given as: 


w T = C f (V S0 I) 1 2 W lf 


(C207A.5-1) 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-33 


s© 

® 1.4 

■H , _ 

> 1.3 



— DURST 


GUST DURATION, sec 

Figure C207A.5-! 

Maximum Speed Averaged over t s to Hourly Mean Speed 


P where C f is a building, component, or structure specific 
coefficient that includes the effects of things like 
building height , building geometry, terrain , and gust 
ifactor as computed using the procedures outlined in 
0fj$CP 2010. F 50 is the 50-year return period design 
iywind speed. W LF is the wind load factor, and / is the 
^importance factor. 

Starting with the nominal return period of 50 years, the 
% yatio of the wind speed for any return period to the 50- 
ifear return period wind speed can he computed from 
fPeterka and Shahid (1998): 


% v t/V$o = [0.36 + 0. lln(127)] 


(C207A.5-2) 


( where T is the return period in years and V T is the T- 
year return period wind speed. The strength design wind 
c load ' W T , occurs when: 


C F Vlo W LF 


(C207A.5-3) 


p V t /V 50 = [0. 36 4- 0. ll?i(127)] (C2Q7A.5-4) 

H =4wZ 


and from Equation C207A.5-4, the return period T 


7 = 0. 00228 exp(l0jWw) (C207A.5-5) 

Using the wind load factor of 1.6 as specified in Section 
207 NSCP 2010, from Equation C207A.5-5 we get 
T ” 709 years; and therefore V design ~ ^709/V^F ** 
^700 Thus for Occupancy Category IV 

structures , the basic wind speed is associated with a 
return period of 700 years, or an annual exceedance 
probability of 0.0014. 

The importance factor used in Section 207 NSCP 2010 
and earlier for the computation of wind loads for the 
design of Occupancy Category I and 11 structures is 
defined so that the nominal 50-year return period non- 
tropical cyclone wind speed is increased to be 
representative of a 100-year return period value. 
Following the approach used above to estimate the 
resulting effective strength design return period 
associated with a 50-year basic design speed, in the case 
of the 100-year return period basic wind speed in the 
non-tropical cyclone-prone regions, we find that: 

T = 00228 exp[lO(K 100 /K 50 )7i4^] (C207A.5-6) 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 



2-34 CHAPTER 2 - Minimum Design Loads 


whereforViQo/Vso computed from Equation C207A.5- 
4 with W if = L6, we find T = 1,697 years. In the 
development of Equation C 7 07 A, 5 -6, the term 
(V 10 Q /V 50 )W if replaces the W LF used in 
Equation €207 A. 5-5, effectively resulting in a higher 
load factor for Occupancy Category 1, 11 and III 
structures equal to ^lfO^ioo/Pso) 2 * Thus for 
Occupancy Category I and II structures, the basic wind 
speed is associated with a return period of 1 , 700 years, 
or an annual exceedance probability of 0,000588, 
Similarly, the 25-year return period wind speed 
associated with Occupancy Category III, IV and V 
buildings equates to a 300-year return period wind 
speed with a wind load factor of LO. 

Wind Speeds . The wind speed maps of Figure 207 A. 5-1 
present basic wind speeds for the entire archipelago of 
the Philippines . The wind speeds correspond to 3 -sec 
gust speeds at 10 m above ground for exposure category 

c 

Serviceability Wind Speeds . For applications of 
serviceability, design using maximum likely events, or 
other applications, it may be desired to use wind speeds 
associated with mean recurrence intervals other than 
those given in Figures 207A.5-1A to 207 A, 5- 1C, To 
accomplish this, previous editions of NSCP 2010 
provided tables with factors that enabled the user to 
adjust the basic design wind speed (previously having a 
return period of 50 years to wind speeds associated with 
other return periods. 


For applications of serviceability, design using 
maximum likely events, or other applications, Appendix 
C presents maps of peak gust wind speeds at 10 m above 
ground in Exposure C conditions for return periods of 
10, 25, 50, and 100 years. 


The probability P n that the wind speed associated with 
a certain annual probability P a will he equaled or 
exceeded at least once during an exposure period of n 
years is given by: 

P n - 1 - (1 - Pa) 71 (C207A.5-7) 


As an example, if a wind speed is based upon P a ~ 0.02 
(50 -year mean recurrence interval), there exists a 
probability of 0.40 that this speed will be equaled or 
exceeded during a 25-year period \ and a 0.64 
probability of being equaled or exceeded in a 50-year 
period. 


Similarly, if a wind speed is based upon P a - 0.00143 
(700-year mean recurrence interval), there exists a 
3.5% probability that this speed will be equaled or 
exceeded during a 25-year period, and a 6.9% i | 
probability > of being equaled or exceeded in a 50-year 
period. 

Some products have been evaluated and test methods 
have been developed based on design wind speeds that 
are consistent with the unfactored load effects typically 
used in Allowable Stress Design. Table C207A.5-6 
provides conversion from the strength design-based 
design wind speeds used in the ASCE 7-10 design wind 
speed maps and the Section 207 NSCP 2010 design wind 
speeds used in these product evaluation reports and test 
methods. A column of values is also provided to allow 
coordination with ASCE 7-93 design wind speeds. 

207A.5.2 Special Wind Regions 

Mountainous terrain, gorges, and special wind regions 
shown in Figure 207A.5-1 shall be examined for unusual 
wind conditions. The authority having jurisdiction shall, if 
necessary, adjust the values given in Figure 207A.5-1 to 
account for higher local wind speeds. Such adjustment! 
shall be based on meteorological information and an 
estimate of the basic wind speed obtained in accordance 
with the provisions of Section 207A.5.3. 

Commentary: 


Although the wind speed map of Figure 207 A. 5- 1 is valid 
for most regions of the country, there are special regions: ) 
in which wind speed anomalies are known to exist. Some off 
these special regions are noted in Figure 207A.5-1. Winds 
blowing over mountain ranges or through gorges or riven 
valleys in these special regions can develop speeds that are : 
substantially higher than the values indicated on the map. 
When selecting basic wind speeds in these special regions f 
use of regional climatic data and consultation with a wind 
engineer or meteorologist is advised. 

It is also possible that anomalies in wind speeds exist on a 
micrometeorological scale. For example , wind speed-up 
over hills and escarpments is addressed iff 
Section 207 A. 8 . Wind speeds over complex terrain may bff 
better determined by wind-tunnel studies as described in 
Section 207 F. Adjustments of wind speeds should be made 
at the micrometeorological scale on the basis of wind- 
engineering or meteorological advice and used In 
accordance with the provisions of Section 207A.5.3 when: 
such adjustments are warranted. Due to the complexity of \ 
mountainous terrain and valley gorges in Hawaii , there \ 
are topographic wind speed-up effects that cannot bff 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-35 



solely by Figure 207A.S-1 (Applied Research 
PS2001). 


2074.5.3 Estimation of Basic Wind Speeds from 
Regional Climatic Data 


|| area $ outside tropical cyclone-prone regions, regional 
Wmmtic data shall only be used in lieu of the basic wind 
itlpeeds given in Figure 207A.5-1 when (1) approved 
Klxtreme-value statistical-analysis procedures have been 
llmployed in reducing the data; and (2) the length of record, 
Sampling error, averaging time, anemometer height, data 
iffflity, and terrain exposure of the anemometer have been 
Sfaken into account. Reduction in basic wind speed below 
IlSMtof Figure 207A.5-1 shall be permitted. 

I Jo tropical cyclone-prone regions, wind speeds derived 
S^fSrbm simulation techniques shall only be used in lieu of the 
§g||j$ib wind speeds given in Figure 207A.5-1 when 
llpproved simulation and extreme value statistical analysis 
procedures are used. 

| In areas outside tropical cyclone-prone regions, when the 
ftSasic wind speed is estimated from regional climatic data, 
fJtHe basic wind speed shall not be less than the wind speed 
ll&sociated with the specified mean recurrence interval, and 
||he estimate shall be adjusted for equivalence to a 3-s gust 
Hiind speed at 10m above ground in Exposure C. The data 
f analysis shall be performed in accordance with this section. 

using regional climatic data in accordance with the 
of Section 207 A. 5. 3 and in lieu of the basic wind 
given in Figure 207A.5-1, the user is cautioned that 
1st factors, velocity pressure exposure coefficients , 
'i^Mifeffect factors , pressure coefficients , and force 
f^^teients of this code are intended for use with the 3-s 
;^^faspeed at 10m above ground in open counify . It is 
necessary, therefore , that regional climatic data based on 
| ^^^rent averaging time, for example, hourly mean or 
fastest mile , he adjusted to reflect peak gust speeds at 10m 
ground in open country. ,-fx. 

■.ffjming local data, it should be emphasized that sampling 
Fad to large uncertainties in specification of the 
jWifdspeed. Sampling errors are the errors associated with 
the limited size of the climatological data samples (years 
Igf^cord^ of annual extremes). It is possible to have a 
A P////V error in wind speed at an individual station with a 
record length of 30 years. While local records of limited 
extent of ten must be used to define wind speeds in special 
wind areas, care and conservatism should be exercised in 
Im^ir'use. 




If meteorological data are used to justify a wind speed 
lower than 1 77-hn/h 700-yr peak gust at 10 m , an' analysis 
of sampling error is required to demonstrate that the wind 
record could not occur by chance . This can - be 
accomplished by showing that the difference between 
predicted speed and 177 km/h contains two to three 
standard deviations of sampling error (Simiu and Scanlan 
1996). Other equivalent methods may be used. 

207A.5.4 Limitation 

Tornadoes have not been considered in developing the 
basic wind-speed distributions. 

207 A.6 Wind Directionality 

The wind directionality factor, K d , shall be determined 
from Table 207A.6-L This directionality factor shall only 
be included in determining wind loads when the load 
combinations specified in Sections 2.3 and 2.4 are used for 
the design. The effect of wind directionality in determining 
wind loads in accordance with Section 207F shall be based 
on an analysis for wind speeds that conforms to the 
requirements of Section 207A.5.3. 

Commentary: 

The wind load factor 1.3 in ASCE 7-95 included a ‘‘wind 
directionality factor” of 0.85 (Ellingwood 1981 and 
Ellingwood et at 1982). This factor accounts for two 
effects: (1) The reduced probability of maximum winds 
coming from any given direction and (2) the reduced 
probability of the maximum pressure coefficient occurring 
for any given wind direction . The wind directionality factor 
(identified as K d in the code) is tabulated in Table 207A.6- 
1 for different structure types. As new research becomes 
available t this factor can be directly modified. Values for 
the factor were established from references in the literature 
and collective committee judgment. The K d value for round 
chimneys , tanks, and similar structures is given as 0 95 in 
recognition of the fact that the wind load resistance may 
not be exactly the same in all directions as implied by a 
value of 1. 0. A value of 085 might be more appropriate if 
a triangular trussed frame is shrouded in a round cover. A 
value of 1.0 might be more appropriate for a round 
chimney having a lateral load resistance equal in all 
directions. The designer is cautioned by the footnote to 
Table 207 A. 6-1 and the statement in Section 207 A. 6, where 
reference is made to the fact that this factor is only to be 
used in conjunction with the load combinations specified 
in Sectiom2ffdnd2ff^ASCE7i6;jff 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-36 CHAPTER 2 - Minimum Design Loads 


207A.7 Exposure 

For each wind direction considered, the upwind exposure 
shall be based on ground surface roughness that is 
determined from natural topography, vegetation, and 
constructed facilities. 

Commentary: 

The descriptions of the surface roughness categories 
and exposure categories in Section 207 A. 7 have been 
expressed as far as possible in easily understood verbal 
terms that are sufficiently precise for most practical 
applications. Upwind surface roughness conditions 
required for Exposures B and D are shown 
schematically in Figures C207A.7-1 and C207A.7-2, 
respectively . For cases where the designer wishes to 
make a more detailed assessment of the surface 
roughness category and exposure category , the 
following more mathematical description is offered for 
guidance (Irwin 2006). The ground surface roughness is 
\ best measured in terms of a roughness length parameter 
called z 0 . Each of the surface roughness categories B 
through D correspond to a range of values of this 
parameter, as does the even rougher category A used in 
previous versions of the code in heavily built-up urban 
areas but removed in the present edition . The range of 
z 0 in meters (m) for each terrain category is given in 
Table C207A.7-L Exposure A has been included in 
Table C207A . 7-1 as a reference that may be useful when 
using the Wind Tunnel Procedure. Further information 
on values ofz 0 in different types of terrain can be found 
in Simiu and Scanlan (1996) and Table C207A.7-2 
based on Davenport et ai (2000) and Wieringa et al. 
(2001). The roughness classifications in Table C207A. 7- 
2 are not intended to replace the use of exposure 
categories as required in the code for structural design 
purposes. However , the terrain roughness 

classifications in Table C207A.7-2 may he related to 
ASCE 7 exposure categories by comparing z Q values 
between Table C207A. 7-1 and C207A. 7-2. For example, 
the z 0 values for Classes 3 and 4 in Table C207A.7-2 
fall within the range of z 0 values for Exposure C in 
Table C207A.7-1. Similarly , the z 0 values for Classes 5 
and 6 in Table C207A.7-2 fall within the range of z 0 
values for Exposure B in Table C 2 07 A. 7-1. 

Research described in Powell et al. (2003), Done lan et 
ai (2004), and Vickery et al. (2008b) showed that the 
drag coefficient over the ocean in high winds in tropical 
cyclones did not continue to increase with increasing 
wind speed as previously believed (e.g, Powell 1980). 
These studies showed that the sea surface drag 
coefficient , and hence the aerodynamic roughness of the 
ocean , reached a maximum at mean wind speeds of 
about 30m/s. There is some evidence that the drag 


coefficient actually decreases (i.e., the sea surface 
becomes aerodynamically smoother) as the wind speed 
increases further (Powell et al 2003) or as the tropical 
cyclone radius decreases (Vickery et al. 2008b). The 
consequences of these studies are that the surface 
roughness over the ocean in a tropical cyclone is 
cons istent with that of exposure D rather than exposure 
C. Consequently, the use of exposure D along the 
tropical cyclone coastline is now required. 

For Exposure B the tabulated values of K z correspond 
to z 0 = 0.2 m, which is below the typical value of 0.3 m, 
whereas for Exposures C and D they correspond to the 
typical value of z 0 . The reason for the difference in 
Exposure B is that this categoty of terrain , which is 
applicable to suburban areas, often contains open 
patches, such as highways, parking lots, and playing 
fields. These cause local increases in the wind speeds at 
their edges. By using an exposure coefficient 
corresponding to a lower than typical value of z 0 , some 
allowance is made for this. The alternative would be to 
introduce a number of exceptions to use of Exposure B 
in suburban areas , which would add an undesirable 
level of complexity. 

The value ofz 0 for a particular terrain can be estimated 
from the typical dimensions of surface roughness 
elements and their spacing on the ground area using an 
empirical relationship, due to Lettau (1969), which is: 

z 0 = 0. 5 H ob ?—■ (C207A. 7-1) 

A 0 b 

H 0 b = overage height of the roughness in 

the upwind terrain 

Bob ~ average vertical frontal area per 

obstruction presented to the wind 

A ob ~ the average area of ground occupied by 
each obstruction, including the open 
area surrounding it 

Vertical frontal area is defined as the area of the 
projection of the obstruction onto a vertical plane 
normal to the wind direction. The area S ob may be 
estimated by summing the approximate vertical frontal 
areas of all obstructions within a selected area of 
upwind fetch and dividing the sum by the number of 
obstructions in the area. The average height H ob may 
be estimated in a similar way by averaging the 
individual heights rather than using the frontal areas. 
Likewise A ob may be estimated by dividing the size of 
the selected area of upwind fetch by the number of 
obstructions in it. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




As an 

single family homes with typical height H ob = 6m, 
vertical frontal area (including some trees on each lot) 
of 1 00m 2 , and ground area per home of } ,000m 2 , then 
z 0 is calculated to be z 0 ~ 0.5 x 20 x 100/1,000 = 
. ' 0.3 m, which falls into exposure category B according to 
Table C2Q7A.7-1. 


Trees and bushes are porous and are deformed by 
strong winds, which reduce their effective frontal areas 
(ESDI), 1993). For conifers and other evergreens no 
) more than 50 percent of their gross frontal area can be 
taken to be effective in obstructing the wind. For 
; deciduous trees and bushes no more than 15 percent of 
their gross frontal area can be taken to be effective in 
obstructing the wind. Gross frontal area is defined in 
l this context as the projection onto a vertical plane 
v (normal to the wind) of the area enclosed by the 
\ envelope of the tree or bush. 

fjio (1992) estimated that the majority of buildings 
/(perhaps as much as 60 percent to 80 percent) have an 
(exposure categoiy corresponding to Exposure B. While 




//suffice far most practical applications , oftentimes the 
'//designer is in need of additional information , 


'for clearings (e.g, large parking lots y freeways, or tree 
/(/clearings) in the othenvise ", normal ” ground surface 
roughness B. The following is offered as guidance for 
these situations: 


Mere ■ S' 


fffhe simple definition of Exposure B given in the body of 
the code, using the surface roughness categoiy 
definition, is shown pictorially in Figure C207A.7-L 
fifihis definition applies for the surface roughness B 
Condition prevailing 800 m upwind with insufficient 
/*' open patches " as defined in the following text to 
disqualify the use of Exposure B. 

An opening in the surface roughness B large enough to 
fffipve a significant effect on the exposure category 






' 

■ 

. 


CHAPTER 2 - Minimum Design Loads 2-37 


determination is defined as an " open patch . ” An open 
patch is defined as an opening greater than or equal to 
approximately 50 m on each side (i.e., greater than 
50 m by 50 m). Openings smaller than this need not be 
considered in the determination of the exposure 
categoiy. 


The effect of open patches of surface roughness C or D 
on the use of exposure categoiy B is shown pictorially 
in Figures C207A. 7-3 and C207A. 7-4. Note that the plan 
location of any open patch may have a different effect 
for different wind directions. 

Aerial photographs, representative of each exposure 
type, are included in the commentary to aid the user in 
establishing the proper exposure for a given site. 
Obviously, the proper assessment of exposure is a 
matter of good engineering judgment. This fact is 
particularly true in light of the possibility that the 
exposure could change in one or more wind directions 
due to future demolition and/or development . 


207A.7.1 Wind Directions and Sectors 

For each selected wind direction at which the wind loads 
are to be determined, the exposure of the building or 
structure shall be determined for the two upwind sectors 
extending 45° either side of the selected wind direction* 
The exposure in these two sectors shall be determined in 
accordance with Sections 207 A. 7. 2 and 207 A. 7. 3, and the 
exposure whose use would result in the highest wind loads 
shall be used to represent the winds from that direction. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-38 


CHAPTER 2 - Minimum Design Loads 


* 




Notes: 

1 . Values are nominal design 3-second gust wind speeds in kilometers per hour at 1 0 m above ground for Exposure C category. 

2. Linear interpolation between contours is permitted. 

3. Islands and coastal areas outside the last contour shall use the last wind speed contour of the coastal area. 

4. Mountainous terrain, gorges, ocean promontories, and special wind regions shall be examined for unusual wind conditions. 

5. Wind speeds correspond to approximately a 1 5% probability of exceedance in 50 years (Annual Exceedance Probability = 0.00333, MR1 = 300 years). 

6. Results are from PAGASA. 

Figure 207A.5-1 A Basic Wind Speeds for Occupancy Category III, IV and V Buildings and Other Structures 
Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 


2-39 


* 



Notes: 

1- Values are nominal design 3-second gust wind speeds in kilometers per hour at 10 m above ground for Exposure C category. 

2. Linear interpolation between contours is permitted. 

2. Islands and coastal areas outside the last contour shall use the last wind speed contour of the coastal area. 

4- Mountainous terrain, gorges, ocean promontories, and special wind regions shall be examined for unusual wind conditions. 

5. Wind speeds correspond to approximately a 7% probability of exceedance in 50 years (Annual Exceedance Probability = 0.00143, MRI = 700 years). 
6- Results are from PAG AS A. 

Figure 207A.5-1B Basic Wind Speeds for Occupancy Category II Buildings and Other Structures 
National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-40 


CHAPTER 2 - Minimum Design Loads 



Notes: 

1. Values are nominal design 3-second gust wind speeds in kilometers per hour at 10 m above ground for Exposure C category. 

2. Linear interpolation between contours is permitted. 

3. Islands and coastal areas outside the last contour shall use the last wind speed contour of the coastal area. 

4. Mountainous terrain, gorges, ocean promontories, and special wind regions shall be examined for unusual wind conditions. 

5. Wind speeds correspond to approximately a 3% probability of exceedance in 50 years (Annual Exceedance Probability = 0.000588, MRI = 1700 
years). 

6. Results are from PAGASA. 

Figure 207A.5-1C Basic Wind Speeds for Occupancy Category I Buildings and Other Structures 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-41 


WIND 


F/i< 18m, d x a 450 m 

For h > 18m, d, > greater of 790 m or 20 h 


BUILDING OR 
OTHER STRUCTURE 



ANY ROUGHNESS ROUGHNESS B 

njriTLRJTJTJluTJT^^ 

L J 




ANY ROUGHNESS 


di 

Figure C2U/A.7-1 

Upwind Surface Roughness Conditions Requires for Exposure B. 



|< > 

di 

(a) 


WIND 


> greater of 790 m or 20 h, and 
d 2 ^ greater of 1 80 m or 20 h 


BUILDING OR 
OTHER STRUCTURE 



ANY ROUGHNESS 


ROUGHNESS D 


ROUGHNESS B AND/OR C 
™JTJTJTJTJTJT^ 


A 

V 


ANY ROUGHNESS 




di 


(b) 


Figure C207A.7-2 

Upwind Surface Roughness Conditions Required for Exposure D, for the Cases with 
(a) Surface Roughness D Immediately Upwind of the Building, and (b) Surface Roughness B and/or C Immediately 

Upwind of the Building 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 





2-42 CHAPTER 2 - Minimum Design Loads 


Table 207 A. 6-1 

Wind Directionality Factor, K d 


Structure Type 

Directionality Factor K d * 

Buildings 


Main Wind Force Resisting System 

0.85 

Components and Cladding 

0.85 

Arched Roofs 

0.85 

Chimneys, Tanks, and Similar Structures 


Square 

0.90 

Hexagonal 

0.95 

Round 

0.95 

Solid Freestanding Walls and Solid 

0.85 

Freestanding and Attached Signs 

Open Signs and Lattice Framework 

0.85 

Trussed Towers 


Triangular, square, rectangular 

0.85 

All other cross sections 

0.95 


* Directionality Factor K d has been calibrated with combinations of loads 
specified in Section 203. This factor shall only be applied when used in 
conjunction with load combinations specified in Sections 203.3 and 203.4. 


207A.7.2 Surface Roughness Categories 

A ground Surface Roughness within each 45° sector shall 
be determined for a distance upwind of the site as defined 
in Section 207A.7.3 from the categories defined in the 
following text, for the purpose of assigning an exposure 
category as defined in Section 207A.7.3. 

Surface Roughness B: Urban and suburban areas, wooded 
areas, or other terrain with numerous closely spaced 
obstructions having the size of single-family dwellings or 
larger. 

Surface Roughness C: Open terrain with scattered 
obstructions having heights generally less than 9 m. This 
category includes flat open country and grasslands. 

Surface Roughness D: Flat, unobstructed areas and water 
surfaces. This category includes smooth mud flats, salt 
flats, and unbroken ice. 


207A.7.3 Exposure Categories 

Exposure B: For buildings with a mean roof height of less 
than or equal to 9 m, Exposure B shall apply where the 
ground surface roughness, as defined by Surface 
Roughness B, prevails in the upwind direction for a 
distance greater than 450 m. For buildings with a mean roof 
height greater than 9 m, Exposure B shall apply where 
Surface Roughness B prevails in the upwind direction for 
a distance greater than 790 m or 20 times the height of the 
building, whichever is greater. 

Exposure C: Exposure C shall apply for all cases where 
Exposures B or D do not apply. 

Exposure D: Exposure D shall apply where the ground 
surface roughness, as defined by Surface Roughness D, 
prevails in the upwind direction for a distance greater than 
1500 m or 20 times the building height, whichever is 
greater. Exposure D shall also apply where the ground 
surface roughness immediately upwind of the site is 
exposure B or C, and the site is within a distance of 180 in 
or 20 times the building height, whichever is greater, from 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-43 


miMfa Exposure D condition as defined in the previous 
jjSll lntence. 

®For a site located in the transition zone between exposure 
3jj|%ate<mries. the category resulting in the largest wind forces 
shall be used. 


xluitc exposure between the preceding 
, permitted in a transition zone provided that it 
is determined by a rational analysis method defined in the 
recognized literature. 


207A.7.4 Exposure Requirements 

iiMommentaiy: 


■■:■■■■ ■:■■■■■ : ' • 






1 




provision in Section 207A.5J requires that a 
'■Mifmcture be designed for winds from all directions . A 
Rational procedure to determine directional wind loads 
follows. Wind load for buildings using Section 
MiOJBAJ and Figures 207B.4-I, 207B.4-2 or 207B.4-3 
determined for eight wind directions at 45° 
'Sfptervals. with four falling along primary building axes 
| shown in Figure C207A.7-5 . For each of the eight 
I directions, upwind exposure is determined for each of 
b'45° sectors, one on each side of the wind direction 
i§mis. The sector with the exposure giving highest loads 
f&^ill be used to define wind loads for that direction. For 
I} fmample f for winds from the north , the exposure from 
§Jff | cior one or eight, whichever gives the higher load, is 
For wind from the east, the exposure from sector 
|j|f | (dor three, whichever gives the highest load, is used. 
|||®r wind coming from the northeast, the most exposed 










of sectors one or two is used to determine full X and y 
loading individually . and then 75 percent of these loads 
are to be applied in each direction at the same time 
according to the requirements of Section 207B.4.6 and 
Figure 2 07 B. 4-8. The procedure defined in this section 
for determining wind loads in each design direction is 
not to be confused with the determination of the wind 
directionality factor K d . The K d factor determined from 
Section 207 A. 6 and Table 207 A. 6- J applies for all 
design wind directions. See Section C207A.6. 


Wind loads for cladding and low-rise buildings elements 
are determined using the upwind exposure for the single 
surface roughness in one of the eight sectors of 
Figure C207A.7-5 that gives the highest cladding 
pressures. 



Figure C207A.7-5 
Determination of Wind Loads 
from Different Directions 


National Structural Code of the Philippines Volume i, 7th Edition, 2015 


CHAPTER 2 - Minimum Design Loads 


BUILDING OR OTHER 
STRUCTURE 


WIND 


SURFACE ROUGHNESS 




LENGTH OF OPEN I 
PATCHES 


X = 1000 in 


“OPEN PATCHES” - OPENINGS > 50 m x 50 m 
d lt d 2 ,_, d t > SO m 
d 1 + d 2 +_ + d i < 200 m 

TOTAL LENGTH OF SURFACE ROUGHNESS B> 800 m 
WITHIN 1000 m OF UPWIND FETCH DISTANCE 


Figure C207A.7-3 

Exposure B with Upwind Open Patches 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




2-46 CHAPTER 2 - Minimum Design Loads 


207A.7A1 Directional Procedure (Section 207B) 

For each wind direction considered, wind loads for the 
design of the MWFRS of enclosed and partially enclosed 
buildings using the Directional Procedure of Section 207B 
shall be based on the exposures as defined in Section 
207A.7.3. Wind loads for the design of open buildings with 
monoslope, pitched, or troughed free roofs shall be based 
on the exposures, as defined in Section 207A.7.3, resulting 
in the highest wind loads for any wind direction at the site. 

207A.7.4.2 Envelope Procedure (Section 207C) 

Wind loads for the design of the MWFRS for all low-rise 
buildings designed using the Envelope Procedure of 
Section 207C shall be based on the exposure category 
resulting in the highest wind loads for any wind direction 
at the site. 

207A.7.4.3 Directional Procedure for Building 
Appurtenances and Other Structures 
(Section 207D) 

Wind loads for the design of building appurtenances (such 
as rooftop structures and equipment) and other structures 
(such as solid freestanding walls and freestanding signs, 
chimneys, tanks, open signs, lattice frameworks, and 
trussed towers) as specified in Section 207D shall be based 
on the appropriate exposure for each wind direction 
considered. 

207A.7.4.4 Components and Cladding (Section 207E) 

Design wind pressures for components and cladding shall 
be based on the exposure category resulting in the highest 
wind loads for any wind direction at the site. 

207 A.8 Topographic Effects 

Commentary: 

As an aid to the designer , this section was rewritten in 
ASCE 7-98 to specify when topographic effects need to be 
applied to a particular structure rather than when they do 
not as in the previous version. In an effort to exclude 
situations where little or no topographic effect exists , 
Condition (2) was added to include the fact that the 
topographic feature should protrude significantly above 
(by a factor of two or more) upwind terrain features before 
it becomes a factor. For example, if a significant upwind 
terrain feature has a height of 10 m above its base elevation 
and has a top elevation of 30 m above mean sea level then 
the topographic feature (hill, ridge , or escarpment) must 
have at least the H specified and extend to elevation 52 m 


mean sea level (30.5 m + [3.22 x 10.7 mj) within the 3.22- 
km radius specified. 

A wind tunnel study by Means et al (1 996) and observation 
of actual wind damage has shown that the affected height 
II is less than previously specified. Accordingly, Condition 
(5) was changed to 4.5 m in Exposure C. 

Buildings sited on the upper half of an isolated hill or 
escarpment may experience significantly higher wind 
speeds than buildings situated on level ground. To account 
for these higher wind speeds, the velocity pressure 
exposure coefficients in Tables 207 B. 3-1, 207 C. 3-1, 
207D.3-1, and 207E.3-1 are multiplied by a topographic 
factor , K zt , determined by Equation 207A.S-L The 
topographic feature (2-D ridge or escarpment, or 3-D 
axisymmetrical hill) is described by two parameters, H and 
L h . H is the height of the hill or difference in elevation 
between the crest and that of the upwind terrain. is the 
distance upwind of the crest to where the ground elevation 
is equal to half the height of the hill. K zt is determined from 
three multipliers, K\, K 2 , and which are obtained from 
Figure 207A.8-1, respectively. is related to the shape 
of the topographic feature and the maximum speed-up near 
the crest, K 2 accounts for the reduction in speed-up with 
distance upwind or downwind of the crest, and 
accounts for the reduction in speed-up with height above 
the local ground surface. 

The multipliers listed in Figure 207 A. 8-1 are based on the 
assumption that the wind approaches the hill along the 
direction of maximum slope , causing the greatest speed-up 
near the crest. The average maximum upwind slope of the 
hill is approximately H/2Lf t , and measurements have 
shown that hills with slopes of less than about 
0.10 (. H/L h < 0.20) are unlikely to produce significant 
speed-up of the wind. For values of H/Lh > 0.5 the 
speed-up effect is assumed to be independent of slope. The 
speed-up principally affects the mean wind speed rather 
than the amplitude of the turbulent fluctuations, and this 
fact has been accounted for in the values ofK x , K 2 , and 
/<3 given in Figure 207A.8-1 . Therefore, values of K zt 
obtained from Figure 207A.8-1 are intended for use with 
velocity pressure exposure coefficients, K h and K z , which 
are based on gust speeds . 

It is not the intent of Section 207 A.8 to address the general 
case of wind flow over hilly or complex terrain for which 
engineering judgment, expert advice, or the Wind Tunnel 
Procedure as described in Section 207F may be required. 
Background material on topographic speed-up effects may 
be found in the literature (Jackson and Hunt 1975, Lemelin 
et al. 1988, and Walmsley et al. 1 986). 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-47 


The designer is cautioned that , at present, the code 
contains no provision for vertical wind speed-up because 
of a topographic effect, even though this phenomenon is 
known to exist and can cause additional uplift on roofs. 
Additional research is required to quantify this effect 
before it can be incorporated into the code. 

207A.8.1 Wind Speed-Up over Hills, Ridges, and 
Escarpments 

Wind speed-up effects at isolated hills, ridges, and 
escarpments constituting abrupt changes in the general 
topography, located in any exposure category, shall be 
included in the design when buildings and other site 
conditions and locations of structures meet all of the 
following conditions: 

111. The hill, ridge, or escarpment is isolated and 
unobstructed upwind by other similar topographic 
features of comparable height for 100 times the height 
of the topographic feature (100f/) or 3.2 km, 
whichever is less. This distance shall be measured 
horizontally from the point at which tire height H of 
the hill, ridge, or escarpment is determined. 


2. The hill, ridge, or escarpment protrudes above the 
height of upwind terrain features within a 3.2-km 
radius in any quadrant by a factor of two or more. 

3. The structure is located as shown in Figure 207A.8-1 
in the upper one-half of a hill or ridge or near the crest 
of an escarpment. 

4. H/L h > 0.2. 

5. H is greater than or equal to 4.5 m for Exposure C and 
D and 18 m for Exposure B. 

207A.8.2 Topographic Factor 

The wind speed-up effect shall be included in the 

calculation of design wind loads by using the factor K zt : 


Kzt = (1 + Kl + +■ K3) 2 


(207A.8-1) 


where K 2 , K 2 , and K 3 are given in Figure 207A.8-1. 

If site conditions and locations of structures do not meet all 
the conditions specified in Section 207A.8.1 then 

K xt = 1 . 0 . 



ESCARPMENT 



2-D RIDGE OR 3-D AXISYMMETRICAL HILL 


Figure 207A.8-1 
Topographic Factor, K zt 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2 “48 CHAPTER 2 - Minimum Design Loads 


Table 207A.8-1 

Topographic Multipliers for Exposure C 


/Ci Multiplier 


2-D 

Ridge 



2-D 

Escarp. 





3-D 

Axisym. 


I< 2 Multiplier 

ri i " ah 


/<T Multiplier 



0.00 

0.26 

0.50 

0.32 

1.00 

0.37 

1.50 

0.42 

2.00 

0.47 

2.50 

0.53 

3.00 

3.50 

4.00 


2-D 

Escarp. 

LOO 

0,88 


0.75 


0.63 

0.50 

0.38 


.25 

.13 

.00 


Other 

Cases 


2-D 

Ridge 


2-D 

Escarp. 

1.00 




3-D 

Axisym. 

Hill 

1.00 



1 . For values of H/L fl> x/L fx and z/L tl other than those shown, linear interpolation is permitted. 

2. For j- > 0.50, assume = 0. 50 for evaluating and substitute 2 H for L ft for evaluating l< 2 and K 3 . 

**l i L h 

3. Multipliers arc based on the assumption that wind approaches the hill or escarpment along the direction of maximum slope. 

4. Notation: 


A* 

Y 

Equations: 


{ “ Height of hill or escarpment relative to the upwind terrain, in meters. 

h - Distance upwind of crest to where the difference in ground elevation is half the height of J 

\ - Factor to account for shape of topographic feature and maximum speed-up effect. 

2 - Factor to account for reduction in speed-up with distance upwind or downwind of crest. 

3 = Factor to account for reduction in speed-up with height above local terrain. 

: = Distance (upwind or downwind) from the crest to the building site, in meters. 

: = Height above ground surface at building site, in meters, 

i = Horizontal attenuation factor. 

' ” Height attenuation factor. 

K zt = (1 + Ki + I< 2 + K 3 ) 2 
K t determined from table below 

*•■(*-£) 

l( 3 = e-r* /L * 


l or escarpment, in meters. 


Hill Shape 

2-dimensional ridges 

(or valleys with negative) 

H in KJW/Lk) 

2- dimensional escarpments 

3- dimensional axisymmetrical hill 


KiimiMi 


Exposure 

y 

Upwind 

Downwind 

B 

C 

D 


of Crest 

of Crest 

1.30 

1.45 

1.55 

3.00 

1.50 

1.50 

0.75 

0.85 

0.95 

2.50 

1.50 

4.00 

0.95 

1.05 

1.15 

4.00 

1.50 

1.50 


Figure 207A.8-2 

Parameters for Speed-Up Over Hills and Escarpments 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 































CHAPTER 2 - Minimum Design Loads 2-49 


207A.9 Gust Effects 

: Commentary: 

' • • 

f/SCP 2001 contains a single gust effect factor of 0,85 
Ifor rigid buildings . As an option , the designer can 
> || corporate specific features of the wind environment 
and building size to more accurately calculate a gust 
effect factor. One such procedure is located in the body 
\ of the standard (Solari 1993a and 1993b). A procedure 
is also included for calculating the gust effect factor for 

• flexible structures. The rigid structure gust factor is 0 
percent to 10 percent lower than the simple, but 

• conservative, value of 0. 85 permitted in the code without 
calculation. The procedures for both rigid and flexible 
structures (1) provide a superior model for flexible 
structures that displays the peak factors g Q and g R and 

' (2) cause the flexible structure value to match the rigid 
structure as resonance is removed. A designer is free to 
use any other rational procedure in the approved 
; literature, as stated in Section 207A.9.5. 



~ 

the fundamental model shape 


- 

(z/Ii)t 

£ 


the mode exponent 

p 

— 

air density 

Cfx 

= 

mean along-wind force coefficient 


= 

modal mass 

rh 



I p(z')4> 2 (z)dz 

J o 

p(z) 

== 

mass per unit height 

K 

— 

(1.65)“/(a + f +1) 

and V% i, 

s the 3-s gust speed at height z. This can 


evaluated by V 2 = b(zf 33) a V, where V is the 3-s gust 
speed in Exposure C at the reference height (obtained 
from Figure 207 A. 5-1); b and a are given in 
Table 207A.9-1. 

RMS Along-Wind Acceleration * The rms along-wind 
acceleration <J x {z) as a function of height above the 
ground surface is given by: 


l The gust effect factor accounts for the loading effects in 
•;|j the along-wind direction due to wind turbulence- 
structure interaction. It also accounts for along-wind 
loading effects due to dynamic amplification for flexible 
f buildings and structures. It does not include allowances 
for across-wind loading effects , vortex shedding, 
instability due to galloping or flutter , or dynamic 
torsional effects. For structures susceptible to loading 
y effects that are not accounted for in the gust effect 
: factor, information should be obtained from recognized 
literature (Kareem 1992 and 1985, Gurley and Kareem 
<1993, Solari 1993a and 1993b, and Kareem and Smith 
21994) or from wind tunnel tests . 

Along-Wind Response. Based on the preceding 
de finition of the gust effect factor, predictions of along 
[ wind response, for example, maximum displacement, 
root-mean-square (rms), and peak acceleration, can he 
made. These response components are needed for 
\ survivability and serviceability limit states. In the 
following, expressions for evaluating these along-wind 
response components are given. 

Maximum Along-Wind Displacement The maximum 
along-wind displacement X max (z) as a function of 
height above the ground surface is given by: 


(C207A.9-2) 

where V 2 is the mean hourly wind speed at height z, m/s: 


— — / z \ s 


(C207A.9-3) 


where b and a are defined in Table 2 07 A. 9-1. 

Maximum Along-Wind Acceleration . The maximum 
along-wind acceleration as a function of height above 
the ground surface is given by: 


~~ Ex&x ( z 0 

0.5772 


Ex “ ItiiyifT) 4* 


yj 2 IniiixT) 


(G207A.9-4) 

(C207A.9-5) 


where T = the length of time over which the minimum 
acceleration is computed, usually taken to be 3, 600 s to 
represent l hour. 


Xmaxiz) 


where 


<l)(z)pBhC fx Vi 

2m 1 (27rn 1 ) 2 


Approximate Fundamental Frequency. To estimate the 
KG (C207A.9-1) dynamic response of structures , knowledge of the 

fiindamental frequency (lowest natural frequency) of the 
structure is essential. This value would also assist in 
determining if the dynamic response estimates are 
necessary. Most computer codes used in the analysis of 
National Structural Code of the Philippines Volume I, 7th Edition, 2015 



2-50 CHAPTER 2 - Minimum Design Loads 


structures would provide estimates of the natural 
frequencies of the structure being analyzed. However , 
for the preliminary design stages some empirical 
relationships for building period T a (T a = 1 fn x ) are 
available in the earthquake chapters of ASCE 7. 
However \ it is noteworthy that these expressions are 
based on recommendations for earthquake design with 
inherent bias toward higher estimates of fundamental 
frequencies (Goel and Chopra 1997 and 1998). For 
wind design applications these values may be 
unconservative because an estimated frequency higher 
than the actual frequency would yield lower values of 
the gust effect factor and concomitantly a lower design 
wind pressure. However \ Goel and Chopra (1997 and 
1 998) also cite lower bound estimates of frequency that 
are more suited for use in wind applications . These 
lower-bound expressions are now given in Section 
207 A. 9. 2; graphs of these expressions are shown in 


on regular buildings , limitations based on height and 
slenderness are required. The effective length L e ff, uses 
a height-weighted average of the along-wind length of 
the building for slenderness evaluation. The top portion 


of the building is most important; hence the height - 
weighted average is appropriate. This method is an 
appropriate first-order equation for addressing 
buildings with setbacks . Explicit calculation of gust 
effect factor per the other methods given in Section 
207A.9 can still be performed. 

Observation from wind tunnel testing of buildings where 
frequency is calculated using analysis software reveals 
the following expression for frequency, appropriate for 
buildings less than about 120 m in height , applicable to 
all buildings in steel or concrete: 


n t = 100/// (m) average value 


(C207A.9-6) 


n i = 75 /H (m) lower bound value (C 207 A. 9-7) 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-51 


Equation €207 A. 9-7 for the lower bound value is 
provided in Section 207 A. 9.2. ; . 


gphsed on fill-scale measurements of buildings under the 
action of wind ' the following expression has been 
proposed for wind applications (Zhou and Kareem 
2001. Zhou t Kijewski, and Kareem 2002): 


m = iso/// 


( C207A.9-8) 


This frequency expression is based on older buildings 
and overestimates the frequency common in U.S. 
construction for smaller buildings less than 120 m in 
height, but becomes more accurate for tall buildings 
/ greater than 120 m in height. The Australian and New 
Zealand Standard AS/NZS 1170.2 , Eurocode ENV 1991- 
2 - 4 , Hong Kong Code of Practice on Wind Effects 
(2004), and others have adopted Equation C207A.9-8 
for all building types and all heights . 

Recent studies in Japan involving a suite of buildings 
under low-amplitude excitations have led to the 
following expressions for natural frequencies of 
buildings (Sataka et al 2003): 

Ijrii — 220/ H(m) (concrete buildings) (C207A.9-9) 


ff|f== 164 /H(m) (steel buildings) 


(C207A.9-10) 


The expressions based on Japanese buildings result in 


general expression given in Equations C207A.9-6 
^through C207A.9-S, particularly since the Japanese 
data set has limited observations for the more flexible 
thuddings sensitive to wind effects and Japanese 
construction tends to be stiffen. 

lEbr cantilevered masts or poles of uniform cross-section 
On which bending action dominates): 

n t = (0.56 /h 2 )T(W/m) (C207A.9-1 1) 


IS 


the mass /unit heights (This formula may be used for 
masts with a slight taper, using average value of El and 
m) (ECCS 1978). 

Jti approximate formula for cantilevered / tapered , 
Nrcular poles (ECCS 1978) is: 


n t ■"== [A/ (2nh 2 )]y/(EI/rn) (C207A.9-12) 

where h is the height, and E, /, and m are calculated 
for the cross-section at the base. A depends on the wall 
thicknesses at the tip and base, e t and and external 
diameter at the tip and base, d t and d b , according to the 
following formula: 

[ H 1 9 “"( W\ ' 

■■■■ (C207A.9-13) 

Equation C207A.9-12 reduces to Equation C207A.9-11 
for uniform masts. For free-standing lattice towers 
(without added ancillaries such as antennas or lighting 
frames) (Standards Australia 1994): 

l lsbo^/Zi 2 (C207A 9-14) 

where w a is the average width of the structure in mand 
h is tower height An alternative formula for lattice 
towers (with added ancillaries) (Wyatt 1984) is: 

= (^) 2/3 (^) 1/2 (C207A.9-15) 

where = tower base width and L N = 270 m for 
square base towers, or 230 rnfor triangular base towers. 

Structural Damping. Structural damping is a measure 
of energy dissipation in a vibrating structure that results 
in bringing the structure to a quiescent state. The 
damping is defined as the ratio of the energy dissipated 
in one oscillation cycle to the maximum amount of 
energy in the structure in that cycle. There are as many 
structural damping mechanisms as there are modes of 
converting mechanical energy into heat. The most 
important mechanisms are material damping and 
interfacial damping: 

In engineering practice, the damping mechanism is 
often approximated as viscous damping because it leads 
to a linear equation of motion. This damping measure, 
in terms of the damping ratio, is usually assigned based 
on the construction material, for example, steel or 
concrete. The calculation of dynamic load effects 
requires damping ratio as an input. In wind 
applications , damping ratios of l percent and 2 percent 
are typically used in the United States for steel and 
concrete buildings at serviceability levels, respectively, 


6.65 


°- 9 + (S) 


0.666 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-52 CHAPTER 2 - Minimum Design Loads 


while ISO (1997) suggests 1 percent and 1.5 percent for 
steel and concrete, respectively . Damping values for 
steel support structures for signs, chimneys, and towers 
may he much lower than buildings and may fall in the 
range of (l 15 percent to 0.5 percent Damping values of 
special structures like steel stacks can be as low as OJ 
percent to 0.6 percent and 0.3 percent to 1.0 percent for 
unlined and lined steel chimneys, respectively (ASME 
1992 and CICIND 1999). These values may provide 
some guidance for design . Damping levels used in wind 
load applications are smaller than the 5 percent 
damping ratios common in seismic applications because 
buildings subjected to wind loads respond essentially 
elastically whereas buildings subjected to design level 
earthquakes respond inelastically at higher damping 
levels. 

Because the level of structural response in the 
serviceability and survivability states is different , the 
damping values associated with these states may differ. 
Further, due to the number of mechanisms responsible 
for damping, the limited full-scale data manifest a 
dependence on factors such as material height \ and type 
of structural system and foundation. The Committee on 
Damping of the Architectural Institute of Japan suggests 
different damping values for these states based on a 
large damping database described in Sataka et ah 
(2003). 

In addition to structural damping, aerodynamic 
damping may he experienced by a structure oscillating 
in air. In general the aerodynamic damping 
contribution is quite small compared to the structural 
damping, and it is positive in low to moderate wind 
speeds. Depending on the structural shape, at some 
wind velocities, the aerodynamic damping may become 
negative, which can lead to unstable oscillations. In 
these cases, reference should be made to recognized 
literature or a wind tunnel study. 

Alternate Procedure to Calculate Wind Loads . 
The concept of the gust effect factor implies that the 
effect of gusts can be adequately accounted for by 
multiplying the mean wind load distribution with height 
by a single factor. This is an approximation. If a more 
accurate representation of gust effects is required, the 
alternative procedure in this section can be used. It 
takes account of the fact that the inertial forces created 
by the building '$ mass, as it moves under wind action, 
have a different distribution with height than the mean 
wind loads or the loads due to the direct actions of gusts 
(ISO 1997 and Sataka et ai 2003). The alternate 
formulation of the equivalent static load distribution 
utilizes the peak base bending moment and expresses it 
in terms of inertial forces at different building levels. A 
base bending moment, instead of the base shear as in 


earthquake engineering \ is used for the wind loads, as it 
is less sensitive to deviations from a linear mode shape 
while still providing a gust effect factor generally equal 
to the gust factor calculated by the Section 207 NSCP 
2010 standard. This equivalence occurs only for 
structures with linear mode shape and uniform mass 
distribution, assumptions tacitly implied in the previous 
formulation of the gust effect factor, and thereby permits 
a smooth transition from the existing procedure to the 
formulation suggested here . For a more detailed 
discussion on this wind loading procedure, see ISO 
(1997) and Sataka et al (2003). 

Along-Witul Equivalent Static Wind Loading . 
The equivalent static wind loading for the mean, 
background , and resonant components is obtained using 
the procedure outlined in the following text. 

Mean wind load component P } at the J th floor level is 
given by: 

Pj ~ qjXC p xAjXG (C207A.9-16) 

where 

j - floor level 

Zj = height of the J th floor above the ground 

level 

qj “ velocity pressure at height Zj 

C p = external pressure coefficient 

G = 0 , 925(1 + 1 .7g v hY x Is the gust 

velocity factor 

Peak background wind load component P at the J th 
floor level is given similarly by: 



(C207A.9 -17) 

where 


Gb = 0 925 ( 1-7/2 Bq< * ) 

0 925 \t + 1.7 g v lrj 


— is the background component of the gust 
effect factor. 


Peak resonant wind load component Prj at the J th floor 
level is obtained by distributing the resonant base 
bending moment response to each level 


Pnj = C Mj m n (C2Q7A.9-18) 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-53 


M/ 'ZWjfyZj 


(C207A.9-19) 


MGn 

M »=-r 


(C207A.9-20) 


M 


Z p ' z '- 


/=l,n 


(C207A9-21) 


where 


J Mj 


m r = 

Wj v:l = - 

n = 
= 

Af 


vertical load distribution factor 

peak resonant component of the base 

bending moment response 

portion of the total gravity load of the 

building located or assigned to level / 

total stories of the building 

first structural mode shape value at level j 

mean base bending produced by mean 

wind load 


G r = 0.925 1 


>1 + 1 . 7g v tJ 


liiiv-Z - is the resonant i component of the gust 
■ effect factor. 

Along- Wind Response . Through a simple static 
0nalySis the peak-building response v alongAvhid 
direction can be obtained by: 






(C207A.9-22) 


where r, r B , and f R = mean, peak background, and 


shear forces, moment, or displacement. Once the 
equivalent static wind load distribution is obtained, any 
response component ; including acceleration " can be 
obtained using a simple static analysis: It is suggested 
that caution must be exercised when combining the 
loads instead of response according to the preceding 
expression, for example, 


'■Pj,= Pj + 




(C207A.9-2 3) 


because the background and the resonant load 
components have normally different distributions along 


the building height. Additional background can be found 
in ISO ( 1997) and Sataka et ah (2003). 

Example: The following example is presented^ to 
illustrate the calculation of the gust effect factor. Table 
C207A.9-1 uses the given information to obtain values 
from Table 2 07 A. 9-1. Table C20 7 A. 9-2 presents the 
calculated values. Table C2 0 7 A.9^3: summarizes the 
calculated displacements and acceleration* ■■■as^-a- 
function of the height Z- 


Given Values: 


Basic wind speed at reference 
height in exposure C 


150 km/h 

c fx 

y \ 

1.3 ';0. 

Damping ratio 

= 

0.01 

Mode exponent 


1.0 

Type of exposure 

. : =V 

5 

Building height h 

v-v.' « ;■ 

183: m f|v 

Building width B 

cim-] 

30.5m: 

Building depth L 


30.5 m 

Building natural frequency n t 

a 

0.2 Hz 

Building density 


12 lb/ft 3 
192.0817 
kg/m 3 

Air density 

= 

1.2369 

kg/m 3 


Table C207A.9-1 
Calculated Values 



National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-54 CHAPTER 2 - Minimum Design Loads 


V 

z 

h 

u 

Q z 

v- z 

h 

N i 
R„ 


Table C207A.9-2 
Calculated Values 


40.23 m/s 
109.73m 
0.201 
216.75 m 
0.616 
32. 95 m/s 
47.59 m/s 
1.31 
0.113 
0.852 


Rb 

V 

Rn 

n 

Rl 

R 2 

Gf 

K 

9r 


0.610 

5.113 

0.176 

2.853 

0.289 

0.813 

1.062 

0.501 

10.88x10 6 
kg 

3.787 


Table 207A.9-3 


Floor 

Zj (m) 

<h 

^maxj 

RMS Acc.* 

( m / s 2 ) 

RMS Acc. * 

(mg) 

Max Acc. * 

( m / s 2 ) 

Max Acc. 

(mg) 

0 

0 

0 

0 

0 

0 

0 

0 

5 

18.29 

0.10 

0.03 

0.00 

0.41 

0.02 

1.6 

10 

36.58 

0.20 

0.06 

0.01 

0.83 

0.03 

3.1 

15 

54.86 

0.30 

0.09 

0.01 

1.24 

0.05 

4.7 

20 

73.15 

0.40 

0.13 

0.02 

1.66 

0.06 

6.3 

25 

91.44 

0.50 

0.16 

0.02 

2.07 

0.08 

7.8 

30 

109.73 

0.60 

0.19 

0.02 

2.49 

0.09 

9.4 

35 

128.02 

0.70 

0.22 

0.03 

2.90 

0.11 

11.0 

40 

146.3 

0.80 

0.25 

0.03 

3.32 

0.12 

12.6 

45 

164.59 

O.SO 

0.28 

0.04 

3.73 

0.14 

14.1 

50 

182.88 

1.00 

0.31 

0.04 

4.14 

0.15 

15.7 


Aerodynamic Loads on Tall Buildings — An 
Interactive Database . Under the action of wind, tall 
buildings oscillate simultaneously in the along-wind, 
across -wind, and torsional directions. While the along- 
wind loads have been successfully treated in terms of 
gust loading factors based on quasi-steady and strip 
theories, the across-wind and torsional loads cannot be 
treated in this manner, as these loads cannot be related 
in a straightforward manner to fluctuations in the 
approach flow. As a result, most current codes and 
standards provide little guidance for the across-wind 
and torsional response ISO (1997) and Sataka et ai 
(2003). 

To provide some guidance at the prelimiruvy design 
stages of buildings , an interactive aerodynamic loads 
database for assessing dynamic wind-induced loads on 
a suite of generic isolated buildings is introduced. 
Although the analysis based on this experimental 
database is not intended to replace wind tunnel testing 
in the final design stages , it provides users a 
methodology to approximate the previously untreated 


across-wind and torsional responses in the early design 
stages. The database consists of high frequency base 
balance measurements involving seven rectangular 
building models , with side ratio D/B, where D is the 
depth of the building section along the oncoming wind 
direction) from 1/3 to 3 , three aspect ratios for each 
building model in two approach flows ; namely , 
BL t (a = 0, 16) andBL 2 (a = 0. 35) corresponding to 
an open and an urban environment. The data are 
accessible with a user-friendly Java-based applet 
through the worldwide Internet community at 
http://aerodata. cejid.edu/interface/interface. html 

Through the use of this interactive portal users can 
select the geometry and dimensions of a model building 
from the available choices and specify an urban or 
suburban condition. Upon doing so, the aerodynamic 
load spectra for the along-wind, across-wind, or 
torsional directions is displayed with a Java interface 
permitting users to specify a reduced frequency 
(building frequency x building dimension/ wind 
velocity) of interest and automatically obtain the 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-55 


. 

\ 


corresponding spectral value . When coupled with the 
{supporting Web documentation, examples, and concise 
analysis procedure , the database provides a 
comprehensive tool for computation of wind-induced 
response of tall buildings, statable as a design guide in 
the preliminary stages . 


. 

; 


Example: An example tall building is used to 
demonstrate the analysis using the database. The 
building is a square steel tall building with size H x W t 
x IV 2 ~ 200 x 40 x 40 m and an average radius of 
gy ration of IS m. 


. 






■ 


j; 

■ 

\ 


The three fundamental mode frequencies, f lt are 0.2, 

0.2, and 035 Hz in X, Y, and Z directions, respectively ; 
I the mode shapes are all linear, or (3 is equal to 1.0, and 
there is no modal coupling. The building density is equal 
to 250 kg/ m*. This building is located in Exposure A or 
close to the Sl 2 test condition of the Internet-based 
database (Zhou et ai 2002), In this location 
(Exposure A), the reference 3-sec design gust speed at a 
50-year recurrence interval is 63 m/s [ASCE 7-98], 
which is equal to 18.9 m/s upon conversion to 1-h mean 
wind speed with 50-yr MRI (207 * 030 = 62 m/s). For 
- serviceability requirements, 1-h mean wind speed with 
' I0-yr MRI is equal to 14 m/s (207 x 030 * 0.74 = 46). 

' For the sake of illustration only, the first mode critical 
structural damping ratio, < r 1 . is to be 0.01 for both 
'survivability and serviceability design. 

. Using these aerodynamic data and the procedures 
) provided on the Web and in ISO (1997), the wind load 
: effects are evaluated and the results are presented in 
Table C207A. 9-4. This table includes base moments and 
acceleration response in the along-wind direction 
; obtained by the procedure in ASCE 7-02. Also the 
building experiences much higher across-wmd load 
effects when compared to the along-wind response for 
this example, which reiterates the significance of wind 
i loads and their effects in t he across -wind direction. 




' ■ 

m 








207A.9.1 Gust Effect Factor 

The gust-effect factor for a rigid building or other structure 
is permitted to be taken as 0*85. 

207A.9.2 Frequency Determination 

To determine whether a building or structure is rigid or 
flexible as defined in Section 207A.2, the fundamental 
natural frequency, n ly shall be established using the 
structural properties and deformational characteristics of 
hie resisting elements in a properly substantiated analysis. 




■ 


Low-Rise Buildings, as defined in 207 A.2, are permitted to 
be considered rigid. 

207A.9.2.1 Limitations for Approximate Natural 
Frequency 

As an alternative to performing an analysis to determine 
n 1 , the approximate building natural frequency, n ly shall 
be permitted to be calculated in accordance with Section 
207A.9.3 for structural steel, concrete, or masonry 
buildings meeting the following requirements: 

1. The building height is less than or equal to 91 m, and 

2. The building height is less than 4 times its effective 
length, L e ff . 


The effective length, L e ff y in the direction under 
consideration shall be determined from the following 
equation: 




I \ 


L eff~ 


Z"=l Mi 

lUhi 


(207A.9-1) 


The summations are over the height of the building 
where 

hi ~ is the height above grade of level i 

Li = is the building length at level i parallel to the 

wind direction 


207A.9.3 Approximate Natural Frequency 

The approximate lower-bound natural frequency (n a ), in 
Hertz, of concrete or structural steel buildings meeting the 
conditions of Section 207A.9.2.1, is permitted to be 
determined from one of the following equations: 

For structural steel moment-resisting-frame buildings: 


n a = 22.2 //i 08 (207A.9-2) 

For concrete moment-resisting frame buildings: 

n a — 43.5//1 0,9 (207 A. 9-3) 

For structural steel and concrete buildings with other 
lateral-force-resisting systems: 

n a = 75/ft (207A.9-4) 


National Structural Code of the Philippines Volume 1, 7th Edition, 2015 


2-56 CHAPTER 2 - Minimum Design Loads 


For concrete or masonry shear wall buildings, it is also 
permitted to use: 


n a = 385 (C w ) os /h (207A.9-5) 


where 



where 

ft = mean roof height (m) 
n = number of shear walls in the building 
effective in resisting lateral forces in the 
direction under consideration 
A b = base area of the structure (m 2 ) 

A = horizontal cross-section area of shear wall 
“i” (m 2 ) 

p. = length of shear wall “i” (m) 
hi ~ height of shear wall “i” (m) 

207A.9.4 Rigid Buildings or Other Structures 


For rigid buildings or other structures as defined in Section 
207A.2, the gust-effect factor shall be taken as 0.85 01 
calculated by the formula: 


G = 


0.925 


rl + 1- 7g q/ z Q\ 
l l + 1.7g v / z ) 


h 



In SI: 


I- Z = c 



(207A.9-6) 


(207A.9-7) 


where I? is the intensity of turbulence at height z 

where z is the equivalent height of the structure defined as 
0. 6/i, but not less than z mi „ for all building heights h. z min 
and c are listed for each exposure in Table 207A.9-1; %q 
and g v shall be taken as 3.4. The background response Q 
is given by: 


Q = 


1 + 0. 63 


(tt) 


0.63 


(207A.9-8) 


where B and h are defined in Section 207 A.3 and L % is the 
integral length scale of turbulence at the equivalent height 
given by: 




(207A.9-9) 


In SI: 


In which £ and e are constants listed in Table 207A.9-1. 

207A.9.5 Flexible or Dynamically Sensitive Buildings 
or Other Structures 

For flexible or dynamically sensitive buildings or other 
structures as defined in Section 207A.2, the gust-effect 
factor shall be calculated by: 


1 + 1. 71 


= 0.925 ! 




(207A.9-10) 


1 + 1. 7g v / z 


gQ and g v shall be taken as 3.4 and g n is given by: 

(207A.9-1 1) 


g n = ,/21n(3600 n x ) 
0.577 

+ - 


72111 ( 3600 ^) 

R, the resonant response factor, is given by: 


R 


-R n R h R B (0.53 + 0A7R L ) 


R 


7. 47 Ni 


n (1 + 10. 3 Ni ) 5 / 3 

.. n i^2 
N 1 = -T7— 


(207A.9-12) 

(207A.9-13) 

(207A.9-14) 


Association of Structural Engineers 


of the Philippines. Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-57 


= for ?7 > 0 (207A.9-15a) 


n 277 2 

R f = 1 


for 77 = 0 (207A.9-15b) 


w j iere the subscript € in Equation 207A.9-15 shall be taken 
as ft. and ft, respectively, where ft, B , and ft are defined 
in Section 207A.3. 


ni 

P 


fundamental natural frequency 
R h setting rj = 4. 6n 1 ft/V 2r 
setting 7] = 4- 6n t B/V^ 

R l setting 77 = 15.4nift/F z 

damping ratio, percent of critical (i.e. for 2% 

use 0.02 in the equation) 

mean hourly wind speed (m/s) at height z 

determined from Equation 207A.9-16: 

<207A ' 9 • 1<i, 


In SI: 




where ft and a are constants listed in Table 207A.9-1 and 
V is the basic wind speed in km/h. 

207A.9.6 Rational Analysis 

In lieu of the procedure defined in Sections 207A.9.3 and 
207A.9.4, determination of the gust-effect factor by any 
rational analysis defined in the recognized literature is 
permitted. 

207A.9.7 Limitations 

Where combined gust-effect factors and pressure 
coefficients (GC p ), (GC pi ), and ( GC p f ) are given in 
figures and tables, the gust-effect factor shall not be 
determined separately. 


207A.10 Enclosure Classification 

Commentary: 

Accordingly , the code requires that a determination be 
made of the amount of openings in the envelope to assess 
enclosure classification ( enclosed , partially enclosed \ or 
open), “ Openings " are specifically defined in this version 
of the code as “ apertures or holes in the building envelope 
which allow air to flow through the building envelope and 
which are designed as “ open ” during design winds . 
Examples include doors , operable windows, air intake 
exhausts for air conditioning and or ventilation systems , 
gaps around doors, deliberate gaps in cladding, and 
flexible and operable louvers . Once the enclosure 
classification is known, the designer enters Table 207 A. 11 - 
1 to select the appropriate internal pressure coefficient 

This version of the code has four terms applicable to 
enclosure: wind-borne debris regions, glazing, impact- 
resistant glazing, and impact protective system. “Wind- 
borne debris regions " are specified to alert the designer to 
areas requiring consideration of missile impact design and 
potential openings in the building envelope . " Glazing ” is 
defined as “any glass or transparent or translucent plastic 
sheet used in windows, doors, skylights, or curtain walls, " 
“Impact resistant glazing >} is specifically defined as 
“ glazing that has been shown by testing to withstand the 
impact of test missiles . " “Impact protective systems'- over 
glazing can be shutters or screens designed to withstand 
wind-borne debris impact Impact resistance of glazing 
and protective systems can be tested using the test method 
specified in ASTM El 886-2005 (2005), with missiles, 
impact speeds, and pass/fail criteria specified in ASTM 
El 996-2009 (2009), Other approved test methods are 
acceptable. Origins of missile impact provisions contained 
in these standards are summarized in Minor (1994) and 
Twisdale et al (1996): : •••.• 

Attention is drawn to Section 2 07 A. 10.3, which requires 
glazing in Category I, II, III , and IV buildings in wind- 
borne debris regions to be protected with an impact 
protective system or to be made of impact resistant glazing. 
The option of unprotected glazing was eliminated for most 
buildings in the 2005 edition of the standard to reduce the 
amount of wind and water damage to buildings during 
design wind storm events , 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-58 CHAPTER 2 - Minimum Design Loads 


Table 207A.9-1 
Terrain Exposure Constants 


Exposure 

a 


a 

b 

a 

b 

c 

^(m) 

€ 

Zmin(m)* 

B 

7.0 

365.76 

1/7 

0.84 

1/4.0 

0.45 

0.30 

97.54 

1/3.0 

9.14 

c 

9.5 

274.32 

1/9.5 

TOO 

1/6.5 

0.65 

0.20 

152.4 

1/5.0 

4.57 

D 

11.5 

213.36 

1/11.5 

1.07 

1/9.0 

0.80 

0.15 

198.12 

1/8.0 

2.13 


* z min - minimum height used to ensure that the equivalent height z is greater of 0.6/t or z min . For buildings with 
h < z min , z shall be taken as z min . 


Prior to the 2002 edition of the standard \ glazing in the 
lower 18 m of Category IL HI, or IV buildings sited in 
wind-borne debris regions was required to be protected 
with an impact protective system, or to be made of 
impact-resistant glazing , or the area of the glazing was 
assumed to be open . Recognizing that glazing higher 
than 18 m above grade may be broken by wind-borne 
debris when a debris source is present, a new provision 
was added in 2002 . With that new provision , aggregate 
surfaced roofs on buildings within 450 m of the new 
building need to be evaluated . For example, roof 
aggregate, including gravel or stone used as ballast that 
is not protected by a sufficiently high parapet should he 
considered as a debris source. Accordingly , the glazing 
in the new building, from 9 m above the source building 
to grade would need to be protected with an impact 
protective system or be made of impact-resistant 
glazing. If loose roof aggregate is proposed for the new 
building, it too should be considered as a debris source 
because aggregate can be blown off the roof and be 
propelled into glazing on the leeward side of the 
building . Although other types of wind-borne debris can 
impact glazing higher than IS m above grade, at these 
higher elevations , loose roof aggregate has been the 
predominate debris source in previous wind events. The 
requirement for protection 9 m above the debris source 
is to account for debris that can be lifted during flight. 
The following references provide further information 
regarding debris damage to glazing: Season et al. 
(1984), Minor (1985 and 1994), Kareem (1986), and 
Behr and Minor (1994). 

Although wind-borne debris can occur in just about any 
condition, the level of risk in comparison to the 
postulated debris regions and impact criteria may also 
be lower than that determined for the purpose of 
standardization. For example, individual buildings may 
he sited away from likely debris sources that would 
generate significant risk of impacts similar in magnitude 
to pea gravel (i.e., as simulated by 2 gram steel balls in 
impact tests) or butt-on 2x4 impacts as required in 
impact testing criteria. This situation describes a 
condition of low vulnerability only as a result of limited 
debris sources within the vicinity of the building. In 


other cases , potential sources of debris may be present, 
but extenuating conditions can lower the risk. These 
extenuating conditions include the type of materials and 
surrounding construction, the level of protection offered 
by surrounding exposure conditions, and the design 
wind speed. Therefore, the risk of impact may differ from 
those postulated as a result of the conditions specifically 
enumerated in the code and the referenced impact 
standards. The committee recognizes that there are 
vastly differing opinions , even within the standards 
committee, regarding the significance of these 
parameters that are not fully considered in developing 
standardized debris regions or referenced impact 
criteria. 

Recognizing that the definition of the wind-borne debris 
regions given in NS CP 2001 (ASCE 7-98) through 
NSCP 2010 (ASCE 7-05) was largely based on 
engineering judgment rather than a risk and reliability 
analysis, the definition of the wind-borne debris regions 
in ASCE 7-10 for Occupancy Category III and IV 
buildings and structures has been chosen such that the 
coastal areas included in the wind-borne debris regions 
defined with the new wind speed maps are 
approximately consistent with those given in the prior 
editions for this risk category. Thus, the new wind speed 
contours that define the wind-borne debris regions in 
Section 207 A. 10.3.1 are not direct conversions of the 
wind speed contours that are defined in NSCP 2010 
(ASCE 7-05) as shown in Table C207A.5-6. As a result 
of this shift, adjustments are needed to the Wind Zone 
designations in ASTM E 1996 for the determination of 
the appropriate missile size for the impact test because 
the Wind Zones are based on the NSCP 2010 (ASCE 7- 
05) wind speed maps. Chapter 6.2.2 of ASTM E 1996 
should be as follows: 

6.2.2 Unless otherwise specified ' select the wind 
zone based on the basic wind speed as follows: 

6.2.2. 1 Wind Zone 1-210 kph < basic wind speed < 
225 kph. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 


2 - 59 .' 


62X2 Wind Zone 2 - 225 kph < basic wind speed < 240 
kph at greater than L6 km from the coastline . The 
coastline shall be measured from the mean high water 
.mark. 

6,2X3 Wind Zone 3 - basic wind speed > 240 kph , or 
basic wind speed > 225 kph and within 1.6 km of the 
coastline . The coastline shall be measured from the 
mean high water mark . 

However , While the coastal areas included in the wind- 
borne debris regions defined in the new wind speed 
maps for Risk Category II are approximately consistent 
with those given in NSCP2010 (ASCE 7-05), significant 
reductions in the wind-borne debris regions for this risk 
category occur in the area around Jacksonville, Florida , 
in the Florida Panhandle, and inland from the coast of 
North Carolina . 

The introduction of separate risk-based maps for 
different risk categories provides a means for achieving 
a more risk-consistent approach for defining wind- 
borne debris regions. The approach selected was to link 
the geographical definition of the wind-borne debris 
regions to the wind speed contours in the maps that 
correspond to the particular risk category . The resulting 
expansion of the wind-borne debris region for 
Occupancy Category I and II buildings and structures 
(wind-borne debris regions in Figure 207 A, 5- 1 C that 
are not part of the wind-borne debris regions defined in 
Figure 207 A J- IB) was considered appropriate for the 
types of buildings included in Occupancy Category I 
and I L A review of the types of buildings and structures 
currently included in Occupancy Category III suggests 
that life safety issues would be most important, in the 
expanded wind- borne debris region . for health care 
facilities . Consequently , the committee chose to apply 
the expanded wind-borne debris protection requirement 
to this type of Occupancy Category III facilities and not 
to all Occupancy Category III buildings and structures. 

207A.10.1 General 

For the purpose of determining internal pressure 
coefficients, all buildings shall be classified as enclosed, 
partially enclosed, or open as defined in Section 207A.2. 

207A.10.2 Openings 

A determination shall be made of the amount of openings 
in the building envelope for use in determining the 
enclosure classification. 


207A.10.3 Protection of Glazed Openings 

Glazed openings in Occupancy Category 1, II, III or IV 
buildings located in tropical cyclone-prone regions shall be 
protected as specified in this Section. 

207A. 10.3.1 Wind-borne Debris Regions 

Glazed openings shall be protected in accordance with 
Section 207A. 10.3.2 in the following locations: 

1. Within 1.6 km of the coastal mean high water line 
where the basic wind speed is equal to or greater than 
58 m/s, or 

2. In areas where the basic wind speed is equal to or 
greater than 63 ni/s. 

For Occupancy Category 111 and IV buildings and 
structures, except health care facilities, the wind-borne 
debris region shall be based on Figure 207A.5-1A. For 
Occupancy Category III health care facilities and 
Occupancy Category II buildings and structures, the wind- 
borne debris region shall be based on Figure 207A.5-1B. 
Occupancy Categories shall be determined in accordance 
with Section 103. 

Exception: 

Glazing located over IS m above the ground and over 9 m 
above aggregate-surfaced- roofs, ineluding roofs with 
gravel or stone ballast . located within 4x0 m of the 
building shall be permuted to he unprotected. 

207A.1 0.3.2 Protection Requirements for Glazed 
Openings 

Glazing in buildings requiring protection shall be protected 
with an impact-protective system or shall be impact- 
resistant glazing. 

Impact-protective systems and impact-resistant glazing 
shall be subjected to missile test and cyclic pressure 
differential tests in accordance with ASTM El 996 as 
applicable. Testing to demonstrate compliance with ASTM 
El 996 shall be in accordance with ASTM El 886. Impact- 
resistant glazing and impact protective systems shall 
comply with the pass/fail criteria of Section 7 of ASTM 
El 996 based on the missile required by Table 3 or Table 4 
of ASTM El 996. 


Exception: 



National Structural Code of the Philippines Volume I, 7th Edition, 2015 


0 CHAPTER 2 - Minimum Design Loads 


izing and impact-protective systems in buildings and 
ictures classified as Occupancy Category 1 in 
ordance with Section 103 shall comply with the 
hanced protection” requirements of Table 3 of ASTM 
)96. Glazing and impact-protective systems in all other 
ictures shall comply with the “basic protection” 
uirements of Table 3 of ASTM El 996. 


ser Note: 

'w wind zones that are specified in ASTM El 996 for 
>e in determining the applicable missile size for the 
ipact test , have to be adjusted for use with the wind 
>eed maps of this code and the corresponding wind- 
vne debris regions , see Section C207A. 10.3.2. 


?A.l(h4 Multiple Classifications 

i building by definition complies with both the “open” 

1 “partially enclosed” definitions, it shall be classified as 
“open” building. A building that does not comply with 
ler the “open” or “partially enclosed” definitions shall 
classified as an “enclosed” building. 

7A.11 Internal Pressure Coefficient 

mmentaiy: 

? internal pressure coefficient values in 
hie 2 07 A. 11-1 were obtained from wind tunnel tests 
athopoidos et al. 1979) and full-scale data (Yea t Is and 
hta 1993). Even though the wind tunnel tests were 
uiucted primarily for low-rise buildings , the internal 
'ssure coefficient values are assumed to be valid for 
idings of any height . The values (GC pi ) = +0.1$ and 
IS are for enclosed buildings. It is assumed that the 
'I ding has no dominant opening or openings and that the 
all leakage paths that do exist are essentially uniformly 
tributed over the buildings envelope . The internal 
? ssure coefficient values for partially enclosed buildings 
lime that the building has a dominant opening or 
?nings. For such a building, the internal pressure is 
kited by the exterior pressure at the opening and is 
ically increased substantially as a result , Net loads, that 
the combination of the internal and exterior pressures, 

? therefore also significantly increased on the building 
faces that do not contain the opening . Therefore, higher 
Cpj) values of +0.55 and -0.55 are applicable to this 
ie. These values include a reduction factor to account 
■ the lack of perfect correlation between the internal 
assure and the external pressures on the building 
faces not containing the opening (Invin 1987 and Beste 
d Cermak 1996). Taken in isolation, the internal 


pressure coefficients can reach values of ±0.8 (or possibly 
even higher on the negative side). 

For partially enclosed buildings containing a large 
unpartitioned space, the response time of the internal 
pressure is increased, and this increase reduces the ability 
of the internal pressure to respond to rapid changes in 
pressure at an opening. The gust factor applicable to the 
internal pressure is therefore reduced. Equation 207 A. IF 
1, which is based on Vickeiy and Bloxham (1992) and 
Irwin and Dunn (1994), is provided as a means of adjusting 
the gust factor for this effect on structures with large 
internal spaces, such as stadiums and arenas. 

Because of the nature of tropical cyclone winds and 
exposure to debris hazards (Minor and Behr 1993), glazing 
located below IS m above the ground level of buildings 
sited in wind- borne debris regions has a widely varying 
and comparatively higher vulnerability to breakage from 
missiles, unless the glazing can withstand reasonable 
missile loads and subsequent wind loading, or the glazing 
is protected by suitable shutters. (See Section C207AJ0for 
discussion of glazing above 18 m. When glazing is 
breached by missiles, development of higher internal 
pressure may result, which can overload the cladding or 
structure if the higher pressure was not accounted for in 
the design. Breaching of glazing can also result in a 
significant amount of water infiltration, which typically 
results in considerable damage to the building and its 
contents (Surry et al. 1977, Reinhold 1982, and Stubbs and 
Perry 1993). 

The influence of compartmentalization on the distribution 
of increased internal pressure has not been researched. If 
the space behind breached glazing is separated from the 
remainder of the building by a sufficiently strong and 
reasonably airtight compartment, the increased internal 
pressure would likely be confined to that compartment. 
However, if the compartment is breached (e.g., by an open 
corridor door or by collapse of the compartment wall), the 
increased internal pressure will spread beyond the initial 
compartment quite rapidly. The next compartment may 
contain the higher pressure, or it too could be breached, 
thereby allowing the high internal pressure to continue to 
propagate. Because of the great amount of air leakage that 
often occurs at large hangar doors, designers of hangars 
should consider utilizing the internal pressure coefficients 
for partially enclosed buildings in Table 207 A. 1 1-1. 

207A.11.1 Internal Pressure Coefficients 

Internal pressure coefficients, (GC pi ), shall be determined 
from Table 207A.U-1 based on building enclosure 
classifications determined from Section 207 A. 1 0. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAP i ER 2 - Minimum Design Loads 2-61 


Table 207A.11-1 

Internal Pressure Coefficient, (GC pi ) 


Main Wind Force Resisting 
System and Components and 
Cladding 

All Heights 

"^Enclosed, Partially Enclosed, and 
Open Buildings 

Walls & Roofs 

Enclosure Classification 

(GC pi ) 

Open Buildings 

0.00 

Partially Enclosed Buildings 

+0.55 

-0.55 

Enclosed Buildings 

+0.18 

-0.18 


Notes: 

1. Plus and minus signs signify pressures acting toward 
and away from the internal surfaces, respectively. 

2. Values of ( GC pi ) shall be used with q z or q h as 
specified. 

3. Two cases shall be considered to determine the critical 
load requirements for the appropriate condition: 

L a positive value of (GC p i) applied to all internal 
surfaces 

ii. a negative value of ( GC pi ) applied to all 
internal surfaces 

207 A.1 1.1.1 Reduction Factor for Large Volume 
Buildings, R t 

For a partially enclosed building containing a single, 
unpartitioned large volume, the internal pressure 
coefficient, (GC pi ), shall be multiplied by the following 
reduction factor, 


Ri — 1.0 or 


= 0.5 


1 +■ 


\ 


1 + 


Vi 


7 A 


< 1.0 (207 A. 1 1-1) 


°g / 


where 

^og 

Vi 


total area of openings in the building 
envelope (walls and roof), in m 2 
unpartitioned internal volume, in m 3 


207B Wind Loads On Buildings — MWFRS 

(Directional Procedure) 

Commentary: 

The Direct ional Procedure is the former ° buildings of all 
heights' 1 provision in Method 2 of NSCP 2010 (ASCE 7- 
05) for MWFRS. A simplified method based on this 
Directional Procedure is provided for buildings up to 49 m 
in height . The Directional Procedure is considered the 
traditional approach in that the pressure coefficients 
reflect the actual loading on each surface of the building 
as a function of wind direction , namely t winds 
perpendicular or parallel to the ridge line . 

207B.1 Scope 

207B.1.1 Building Types 

This chapter applies to the determination of MWFRS wind 
loads on enclosed, partially enclosed, and open buildings 
of all heights using the Directional Procedure. 

L Part 1 applies to buildings of all heights where it is 
necessary to separate applied wind loads onto the 
windward, leeward, and side walls of the building to 
properly assess the internal forces in the MWFRS 
members. 

2. Part 2 applies to a special class of buildings designated 
as enclosed simple diaphragm buildings, as defined in 
Section 207A.2, with h < 48 m. 

207B.1.2 Conditions 

A building whose design wind loads are determined in 
accordance with this chapter shall comply with all of the 
following conditions: 

1 . The building is a regular-shaped building or structure 
as defined in Section 207A.2. 

2. The building does not have response characteristics 
making it subject to across-wind loading, vortex 
shedding, instability due to galloping or flutter; or it 
does not have a site location for which channeling 
effects or buffeting in the wake of upwind obstructions 
warrant special consideration. 


National Structural Code of the Philippines Volume L 7th Edition, 2015 


2-62 CHAPTER 2 - Minimum Design Loads 


207B.1.3 Limitations 

The provisions of this chapter take into consideration the 
load magnification effect caused by gusts in resonance with 
along-wind vibrations of flexible buildings. Buildings not 
meeting the requirements of Section 207B.1.2, or having 
unusual shapes or response characteristics shall be 
designed using recognized literature documenting such 
wind load effects or shall use the wind tunnel procedure 
specified in Section 207F. 

207B.L4 Shielding 

There shall be no reductions in velocity pressure due to 
apparent shielding afforded by buildings and other 
structures or terrain features. 


Part 1: Enclosed, Partially Enclosed, and Open 
Buildings of AH Heights 

207B.2 General Requirements 

The steps to determine the wind loads on the MWFRS for 
enclosed, partially enclosed and open buildings of all 
heights are provided in Table 207B.2-1 . 


User Note: 

Use Part 1 of Section 207 B to determine wind pressures 
on the MWFRS of enclosed, partially enclosed or an 
open building with any general plan shape \ building 
height or roof geometry that matches the figures 
provided . These provisions utilize the traditional " all 
heights ” method (Directional Procedure) by calculating 
wind pressures using specific wind pressure equations 
applicable to each building surface . 


207BJL1 Wind Load Parameters Specified in Section 
207A 

The following wind load parameters shall be determined in 
accordance with Section 207A: 

• Basic Wind Speed, V (Section 207A.5) 

© Wind directionality factor, K d (Section 207A.6) 

© Exposure category (Section 207A.7) 

© Topographic factor, K zt (Section 207 A. 8) 

© Gust-effect factor (Section 207A.9) 

© Enclosure classification (Section 207A. 10) 

© Internal pressure coefficient, (GC pi ) 

(Section 207A.1 1) 

207B.3 Velocity Pressure 

207B.3.1 Velocity Pressure Exposure Coefficient 

Based on the exposure category determined in Section 
207A.7.3, a velocity pressure exposure coefficient K z or 
K h , as applicable, shall be determined from Table 207B.3- 
L For a site located in a transition zone between exposure 
categories that is near to a change in ground surface 
roughness, intermediate values of K z or K /t , between those 
shown in Table 207B.3-1 are permitted provided that they 
are determined by a rational analysis method defined in the 
recognized literature. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-63 


. 




Table 207B.2-1 

Steps to Determine MWFRS Wind 
Loads for Enclosed, Partially Enclosed and Open 
Buildings of All Heights 








'■ 

'■ 


BMW'S 












lllllll il:;; 








Step 1: Determine risk category of building or other 
structure, see Table 103-1 

Step 2: Determine the basic wind speed, F, for the 
applicable risk category, see Figure 207A.5- 
| , 1A, BorC 

Step 3: Determine wind load parameters: 

> Wind directionality factor, K d , see 
Section 207 A. 6 and Table 207 A. 6-1 

> Exposure category, see Section 207A.7 

> Topographic factor, K zt , see 
Section 207A.S and Table 207A.8-1 

> Gust Effect Factor, G , see Section 207A.9 

> Enclosure classification, see 
Section 207A.10 

> Internal pressure coefficient, ( GC pi ), see 
Section 207A. 1 1 and Table 207A. 11-1 

Determine velocity pressure exposure 
coefficient, K z or K /n see Table 207B.3-1 


Step 4: 


Step 5: 


Step 6: 


Step 7: 


Determine velocity 
Equation 207B.3-1 


pressure q 7 or q h 


Determine external pressure coefficient, C p or 

C N 

> Figure 207B.4-1 for walls and flat, gable, 
hip, monoslope or mansard roofs 

> Figure 207B.4-2 for domed roofs 

> Figure 207B.4-3 for arched roofs 

> Figure 207B.4-4 for monoslope roof, 
open building 

> Figure 207B,4-5 for pitched roof, open 
building 

> Figure 207B.4-6 for troughed roof, open 
building 

> Figure 207B.4-7 for along-ridge/valley 
wind load case for monoslope, pitched or 
troughed roof, open building 

Calculate wind pressure, p, on each building 

surface 

> Equation 207B.4-1 for rigid buildings 

> Equation 207B.4-2 for flexible buildings 

> Equation 207B.4-3 for open buildings 


Commentary: 

The velocity pressure exposure coefficient K z can be 
obtained using the equation: 




, z 

2.01 — 


2/a 


For 4.57m < (C207B. 


Z<Zc 


2,01 


4. 57 


2 / 


Forz < 4.57 m 


3-1) 

(C207B. 

3-2) 


in which values of a and z g are given in Table 207A.9-1. 
These equations are now given in Tables 207 B 3-1, 
207C3-1, 20703-1 and207E.3-l to aid the user . 

Changes were implemented in NSCP 2001 (ASCE 7-98), 
including truncation of K z values for Exposures A and B 
below heights of 30 m and 9 m, respectively , applicable to 
Components and Cladding and the Envelope Procedure . 
Exposure A was eliminated in the 2002 edition of ASCE 7. 

In the NSCP 2010 (ASCE 7-05) standard , the K z 
expressions were unchanged from NSCP 2001 (ASCE 7- 
98). However, the possibility of interpolating between the 
standard exposures using a rational method was added in 
the NSCP 2010 (ASCE 7-05) edition. One rational method 
is provided in the following text. 

To a reasonable approximation , the empirical exponent a 
and gradient height z g in the preceding expressions 
(Equations C207B3-1 and C207B3-2) for exposure 
coefficient K z may be related to the roughness length z 0 
(where z 0 is defined in Section 0207 A .7) by the relations 


a = c t z 0 


- 0.133 


and 


where 


z g~ C 2 z O 


0.125 


(C207B3-3) 


(C207B3-4) 


Units of z 0 , z g 


m 


Cl 

5.65 


c 2 

450 


■ 


mmy: 

into 


The preceding relationships are based on matching the 
ESDU boundary layer model (Harris and Deaves 1981 and 
ESDU 1990 and 1993) empirically with the power law 
relationship in Equations C207B3-1 and C207B3-2, the 
ESDU model being applied at latitude 35° with a gradient 


National Structural Code of the Philippines Volume 1, 7th Edition, 2015 


2-64 CHAPTER 2 - Minimum Design Loads 


wind of 75 m/s . If z 0 has been determined for a particular 
upwind fetch , Equations C2Q7B3-1 through C207B.3-4 
can be used to evaluate K z . The correspondence between 
z 0 and the parameters a and z„ implied by these 
relationships does not align exactly with that described in 
the commentary to ASCE 7-95 and 7-9S. However ; the 
differences are relatively small and not of practical 
consequence* The ESDU boundary layer model has also 
been used to derive the following simplified method (Irwin 
2006) of evaluating K z following a transition from one 
surface roughness to another. For more precise estimates 
the reader is referred to the original ESDU model (Harris 
and Deaves 1981 and ESDU 1990 and 1993). 

In uniform terrain the wind travels a sufficient distance 
over the terrain for the planetary boundary layer to reach 
an equilibrium state . The exposure coefficient values in 
Table 207B.3-1 are intended for this condition . Suppose 
that the site is a distance x miles downwind of a change in 
terrain : The equilibrium value of the exposure coefficient 
at height z for the terrain roughness downwind of the 
change will be denoted by K zd> and the equilibrium value 
for the terrain roughness upwind of the change will be 
denoted by K zw The effect of the change in terrain 
roughness on the exposure coefficient at the site can be 
represented by adjusting K zd by an increment AK, thus 
arriving at a corrected value K z for the site . 


K z = K zd T AK (C207B.3-5) 


In this expression AK is calculated using: 

AK = (K 33 , u - K 334 ) Ell. Fak ( x ) (C207B.3-6) 

,d 

\AK\ < | K zu - K zd | 

where K 33d and K 33u are respectively the downwind and 
upwind equilibrium values of exposure coefficient at 10 m 
height , and the function F AK (x) is given by: 

FjucW = log 10 @ /log 10 (^) (C207B.3-7) 

For x 0 < x < x x 

F ak {x) = 1 forxCXo 


Fak( x ) 


0 for x > x t 


In the preceding relationships 

2 

Xq = C 3 XlO"( ,f 33,‘|-^33.u) -2-3 


(C207B.3-8). | 


The constant c 3 = 1.0 km. The length x t = 10 km Jbfgi 
K 334 < K 33 u (wind going from smoother terrain upwinM 
to rougher terrain downwind) or X\ = 100 km) for K 334 yy 
K 33u (wind going front rougher terrain upwind toff 
smoother terrain downwind). 


The above description is in terms of a single roughnes . |J 
change. The method can be extended to multiple roughness f 
changes. The extension of the method is best described byfi 
an example. Figure C207B.3-1 shows wind with an initial j§ 
profile characteristic of Exposure D encountering anK 
expanse ofB roughness, followed by a further expanse q|j| 
D roughness and then some more B roughness agaidjf) 
before it arrives at the building site. This situation «|| 
representative of wind from the sea flowing over an outer §| 
strip of land, then a coastal waterway, and then some J| 
suburban roughness before arriving at the building site, ft. 
The above method for a single roughness change is first 
used to compute the profile of K z at station l in 1" igure 
C207B.3-L Call this profile K { z \ The value of AK for the | 
transition between stations l and 2 is then determined | 
using the equilibrium value of K 33u for the roughness | 
immediately upwind of station /, /. as though the | 
roughness upwind of station l extended to infinity . ThiSf 
value of AK is then added to the equilibrium value K\ ' of\ 
the exposure coefficient for the roughness between stations J 
1 and 2 to obtain the profile of K 7 at station 2, which we > 
will call K^\ Note however, that the value of K^ z ] in this \ 
way cannot be any lower than K z l \ The process is then : 
repeated for the transition between stations 2 and 3. Thus , ' 
AK for the transition from station 2 to station 3 is 
calculated using the value of K 33 u for the equilibrium 
profile of the roughness immediately upwind of station 2, y 
and the value of K 33>d for the equilibrium profile of the | 
roughness downwind of station 2 . This value of AK is then 
added to ft^ 2) to obtain the profile K^ at station 3, with 
the limitation that the value of cannot be any higher 
than K^\ 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAP ! ER 2 •“ Minimum Design Loads 2-65 


© 


“W" 


© ® Building 
. . Site 


_jijnrbnTui_ 


^njinjirJ InjiiinruTimrui 


Roughness Roughness Roughness 

||§'©-" 0 B OB 

Figure C207B.3-1 

^||||fe^ Multiple Roughness Changes Due to 
Coastal Waterway 

Mp;-; 

/. s/>?e/e roughness change: Suppose the building 





for //><? open ter rain 

11111= CtZo " 0133 = 6.62 

XO. 066-° 133 


z 0 = 
and 


= 9.5 


0 125 


1,273 

XO. 066° 125 


= 275 /« 


applying Equation C 207 B. 3-1 at 20 m and 10 

mm^hetghis. 


K zu = 2 


/ 66 \ 
01 \906/ 


2/9.5 




l< 33 , „ = 2.01 


(— ) 

\906/ 


2/9.5 


= 1.16 and 


= /.0 


pSp:' 

|||Sj§ Similarly, for the suburban terrain 


“©fafcjZo- 0 - 133 = 6. 62x1. 0~° 133 


llrs//:- 


= 6.62 

^-c 2 z 0 0125 = 1,2 73x1.0° 125 = 388 m 

l|g | therefore 


m?A \ 


Wim 




, 66 x 2/619 

K zll = 2.01 — — 
'1,273/ 

33 \ 2 7 662 


= 0.77 and 


201 y 

gg|.|#r<wi Equation C207B.3-S 

x o = C 3 X 10 - ^ 33d- ^ 33 .“) 2-2 ' 3 


= 0.57 


■ . ; v 

lii©!©;'.- 


= o.62ixio-(° 62 - 100)2 - 23 

= 0.00241 mi 

From Equation C207B.3-7 

/ 6 . 21 \ / / 6.21 \ 

“ ,0gl ° (o.36// 10§10 (o.0024l) = ° 36 

Therefore from Equation C207B.3-6 

0. 82 

dtf = (1. 00 - 0. 67) 0. 36 = 0. 15 

Note that because \AK\ is 0.15, which is less than the 0.3S 
value of\K 33n ~~ K^ id \, 0.15 is retained. Finally , from 
Equation C207B.3-5 , the value ofK z is: 

K z = K zd + AK = 0.82 + 0. 15 = 0. 97 


Because the value 0.97 for K z lies between the values 0.SS 
and 1.16, which would be derived from Table 207 B. 3-1 for 
Exposures B and C respectively, it is an acceptable 
interpolation. If it falls below the Exposure B value , then 
the Exposure B value of K z is to be used. The value K z » 
0.97 may be compared with the value LI 6 that would be 
required by the simple 792 m fetch length requirement of 
Section 207A.7.3. 

The most common case o f a single roughness change where 
an interpolated value of K z is needed is for the transition 
from Exposure C to Exposure B, as in the example just 
described. For this particular transition, using the typical 
values of Zq of 0.02 m and 0.3 m, the preceding formulae 
can be simplified to: 


K z = ( 1 -I- 0. 146 log jo (fff (C207B.3-9) 

I< zB <K z < K zC 


where x is in miles , and K zd is computed using a = 6.62. 
K 2B and K zC are the exposure coefficients in the standard 
Exposures C and B, Figure C 207 B. 3-2 illustrates the 
transition from terrain roughness C to terrain roughness B 
from this expression. Note that it is acceptable to use the 
typical z 0 rather than the lower limit for Exposure B in 
deriving this formula because the rate of transition of the 
wind profiles is dependent on average roughness over 
significant distances , not local roughness anomalies. The 
potential effects of local roughness anomalies , such as 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-66 CHAPTER 2 - Minimum Design Loads 


parking lots and playing fields, are covered by using the 
standard Exposure B value of exposure coefficient, K 2B , as 


Example 2j Multiple Roughness Change Suppose we have 
a coastal waterway situation as illustrated in Figure 
C207B.3-1, where the wind comes from open sea with 
roughness type D, for which we assume z 0 = 0. 003 m, 
and passes over a strip of land 1.61 km wide, which is 
covered in buildings that produce typical B type roughness, 
i.e. z 0 = 0. 3 m . It then passes over a 3.22-km wide strip 
of coastal waterway where the roughness is again 
characterized by the open water value z 0 = 0. 003 m. It 
then travels over 0.16 km of roughness type B (z 0 = 0.3 m 
before arriving at the site, station 3 in Figure C207B.3-1, 


where the exposure coefficient is required at the IS- fiL. 
height. The exposure coefficient at station 3 at 15 m heightf 
is calculated as shown in Table C207B.3-1 . 


■ 


The value of the exposure coefficient at 15 m at station 3 iff 
seen from the table to be 1.067 . This is above that fdff 
Exposure B, which would be 0.81, but well below that fd$$ 
Exposure D, which would be 1.27, and similar to that fa jfp 
Exposure C, which would be 1.09. 





EXP. C, x = 0 km * 


x - 0.08 km 


x - 0.32 km 


x — 0.80 km 


x = 1.60 km 


EXP. 8 


Figure C 2 07 B. 3-2 

Transition from Terrain Roughness C to Terrain Roughness B, Equation C207B. 3.1-9 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-67 


Table C207B.3-1 
Tabulated Exposure Coefficients 


Transition from sea to station 1 

K to, « 

1.215 

K 104 

0.667 

K 15, d 
0.755 

f ak 

0.220 

ak 15 

0.137 

K m 

l\ 7 

0.8 95 

Transition from sea to station 2 

1^10, u 

K lO.d 

fi'is.d 


AKi 5 

K? 


0.667 

L215 

1.215 

0.324 

- 0.190 

1.111 

Transition from sea to station 3 

K io* 

K 10, d 

K l 5 , d 

Fak 

AKis 

4 3) 


1.215 

0.667 

0.667 

0.498 

0.310 

1.067 


Note: The equilibrium values of the exposure coefficients , K t0u , K 10d and K tsd (downwind value of K z at 15 m), were 
calculated from Equation C2Q7B-1 using a and z g values obtained from Equations C207B-3 and C207B-4 with the 
roughness values given. Then F^ K is calculated using Equations C207B-7 and C207B-8, and then the value of AK at 15 m 
height , AK 1S , is calculated from Equation C207B-6 . Finally , the exposure coefficient at 15 in at station i, is obtained 
(from Equation C207B-5. 


207B.3.2 Velocity Pressure 

Velocity pressure, q z , evaluated at height z shall be 
calculated by the following equation: 

q z = 0. 613K z K zt I< d V 2 (Wm 2 )\V in m/s (207B.3-1) 


where 


K d = 

wind directionality factor, see 

Section 207A.6 

K* = 

velocity pressure exposure coefficient, see 
Section 207B.3.1 

= 

topographic factor defined, see 

Section 207A.8.2 

V 

basic wind speed, see Section 207A.5 

Qz = 

velocity pressure calculated using 
Equation 207B.3-1 at height z 

Qzt ~ 

velocity pressure calculated using 
Equation 207B.3-1 at mean roof height h 


The numerical coefficient 0.613 shall be used except where 
sufficient climatic data are available to justify the selection 
of a different value of this coefficient for a design 
application. 


Commentary: 

The basic wind speed is converted to a velocity pressure 
q 7 in (N/m 2 ) at height z by the use of Equation 2Q7B.3- 

L •••• • ••• . • ' 

The constant 0.613 refects the mass density of air for 
the standard atmosphere , that is t temperature of 15 °C 
and sea level pressure of 101:325 kPa t and dimensions 
associated with wind speed in m/s * The constant is 
obtained as follows: 

constant - 1/2[(1.225 kg/m 2 )f (9. 81 m/s 2 )] * 

[(m/s)] 2 [9.81 N/kg] 

- 0.613 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 



2-68 CHAPTER 2 - Minimum Design Loads 


207B.4 Wind Loads — Main Wind Force-Resisting 
System 

207B.4.1 Enclosed and Partially Enclosed Rigid 
Buildings 

Design wind pressures for the MWFRS of buildings of all 
heights shall be determined by the following equation: 


p = qGC p - qi(GC pi ) (N/m 2 ) (207B.4-1) 


where 

q 

q 


qi 


q. 


G 

c v 

(GC pi ) 


q z for windward walls evaluated at 

height z above the ground 

qi t for leeward walls, side walls, and 

roofs, evaluated at height h 

q h for windward walls, side walls, 

leeward walls, and roofs of enclosed 

buildings and for negative internal 

pressure evaluation in partially enclosed 

buildings 

q z for positive internal pressure 
evaluation in partially enclosed buildings 
where height z is defined as the level of 
the highest opening in the building that 
could affect the positive internal 
pressure. For buildings sited in wind- 
borne debris regions, glazing that is not 
impact resistant or protected with an 
impact resistant covering shall be treated 
as an opening in accordance with Section 
207A.10.3. " 

For positive internal pressure evaluation, 
q t may conservatively be evaluated at 
height h(q t ~ q h ) 

gust-effect factor, see Section 207A.9 
external pressure coefficient from 
Figures 207B.4-1, 207B.4-2 and 207B.4- 
3 

internal pressure coefficient from 
Table 207AT1-1 


q and q t shall be evaluated using exposure defined in 
Section 207A.7.3. Pressure shall be applied simultaneously 
on windward and leeward walls and on roof surfaces as 
defined in Figures 207B.4-1, 207B.4-2 and 207B.4-3. 


The numerical constant of 0.613 should be used except 
where sufficient weather data are available to justify a 
different value of this constant for a specific design 
application. The mass density of air will vary as a function 
of altitude, latitude, temperature, weather, and season. 
Average and extreme values of air density are given in 
Table C207B.3-2. 


Table 207B.3-1 

Velocity Pressure Exposure Coefficients, K h and I( z 
Main Wind Force Resisting System - Part 1 


Height above 
ground level, z 

Exposure 

(m) 

B 

C 

D 

0 

1 

4^ 

i/\ 

057 

0.85 

1.03 

6.0 

0.62 

0.90 

1.08 

7.5 

0.66 

0.94 

1.12 

9.0 

0.70 

0.98 

1.16 

12.0 

0.76 

1.04 

1.22 

15.0 

0.81 

1.09 

1.27 

18.0 

0.85 

1.13 

1.31 

21.0 

0.89 

1.17 

1.34 

24.0 

0.93 

1.21 

1.38 

27.0 

0.96 

1.24 

1.40 

30.0 

0.99 

1.26 

1.43 

36.0 

1.04 

1.31 

1.48 

42.0 

1.09 

1.36 

1.52 

48.0 

1.13 

1.39 

1.55 

54.0 

1.17 

1.43 

1.58 

60.0 

1.20 

1.46 

1.61 

75.0 

1.28 

1.53 

1.68 

90.0 

1.35 

1.59 

1.73 

105.0 

1.41 

1.64 

1.78 

120.0 

1.47 

1.69 

1.82 

135.0 

1.52 

1.73 

1.86 

150.0 

1.56 

1.77 

1.89 


Notes: 


1 . The velocity pressure exposure coefficient K z , may be 
determined from the following formula: 

For 4.5 m < z < z g For z < 4.5 m 

I< 7 = 2. Ol(z/z g ) 2/ “ Ky = 2. 01(4. 5 /z g ) 2/ " 

2. a and z g are tabulated in Table 207A.9. 1 . 

3. Linear interpolation for intermediate values of height 
z is acceptable. 

4. Exposure categories are defined Section 207A.7. 
Commentary : 

Loads on Main Wind-Force Resisting Systems: In 
Equations 2Q7B.4-1 and 207BA-2 , a velocity pressure 
term qi appears that is defined as the *' velocity pressure 
for internal pressure determination . ” The positive 
internal pressure is dictated by the positive exterior 
pressure on the windward face at the point where there 
is an opening . The positive exterior pressure at the 
opening is governed by the value of q at the level of the 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2~69 


fffpening, not <\\ v For positive internal pressure 
I evaluation , qi may conservatively be evaluated at height 
h(q i = q h ). For low buildings this does not make much 
difference, but for the example of a 90-m tall building in 
Exposure B with a highest opening at 18 m, the 
^difference between q 90 and q 1Q represents a 59 percent 
idherease in internal pressure . This difference is 
unrealistic and represents an unnecessaty degree of 
fppmervatism. Accordingly, q t = q h for positive 
f internal pressure evaluation in partially enclosed 
fffuildings where height z is defined as the level of the 
1 Highest opening in the building that could affect the 
positive internal pressure , For buildings sited in wind - 
f borne debris regions, with glazing that is not impact 
% resistant or protected with an impact protective system, 
should be treated on the assumption there will be an 
opening. 

Figure 207 B. 4-1. The pressure coefficients for 
MWFRSs are separated into two categories: 

|p! Directional Procedure for buildings of all heights 
fp (Figure 207BA-1) as specified in Section 207Bfor 
Jj buildings meeting the requirements specified 
' therein. 

Envelope Procedure for low-rise buildings having 
fi a height less than or equal to IS m (Figure 207C.4- 
l§|§, 1) as specified in Section 207C for buildings 
3! meeting the requirements specified therein. 


fin generating these coefficients, two distinctly different 
(approaches were used. For the pressure coefficients 
(given in Figure 207 B. 4-1, the more traditional approach 
f$f m followed and the pressure coefficients reflect the 
actual loading on each surface of the building as a 
function of wind direction; namely, winds perpendicular 
or parallel to the ridge line . Observations in wind tunnel 
(tests show that areas of very low negative pressure and 
(even: slightly positive pressure can occur in all roof 
(structures, particularly as the distance from the 
Windward edge increases and the wind streams reattach 
fid: the surface. These pressures can occur even for 
t relatively flat or low slope roof structures. Experience 


and judgment from wind tunnel studies have been used 
to specify either zero or slightly negative pressures 
(-0.18) depending on the negative pressure coefficient. 
These values require the designer to consider a zero or 
slightly positive net wind pressure in the load 
combinations of Section 203. 

Table C207B.3-2 

Ambient Air Density Values for Various Altitudes 


Altitude 

Ambient Air Temperature 

Meters 

Minimum 

Average 

Maximum 

(kg/m 3 ) 

(kg/m 3 ) 

(kg/m 3 ) 

0 

1.1392 

1.2240 

1.3152 

305 

1.1 088 

1.1872 

1.2720 

610 

1.0800 

1.1520 

L2288 

914 

1.0512 

1.1184 

1.1888 

WOO 

1.0432 

1.1088 

1.1776 

1219 

1.0240 

1.0848 

1.1488 

1524 

0.9984 

1.0544 

1.1120 

1829 

0.9728 

1.0224 

1.0752 

2000 

0.9584 

1.0064 

1.0560 

2134 

0.9472 

0.9920 

1.0400 

2438 

0.9232 

0.9632 

1.0048 

2743 

0.8976 

0.9344 

0.9712 

3000 

0.8784 

0.9104 

0.9456 

3048 

0.S752 

0.9072 

0.9408 


National Structural Code of the Philippines Volume L 7th Edition, 2015 



2-70 CHAP i ER 2 - Minimum Design Loads 



Figure C207B.4-1 

Application of Minimum Wind Load 


Figure 207 B. 4-2. Frame loads on dome roofs are adapted 
from the Eurocode (1995). The loads are based on data 
obtained in a modeled atmospheric boundary-layer flow 
that does not fully comply with requirements for wind- 
tunnel testing specified in this code (Blessman 1971). 
Loads for three domes ( h D /0 = O.S,f/D = O.S),(h D / 
D = 0, f/D = 0.5), and ( hD/D = 0 J/D = 0.33) are 
roughly consistent with data of Taylor (1991), who used an 
atmospheric boundaty layer as required in this code . Two 
load cases are defined \ one of which has a linear variation 
of pressure from A to B as in the Eurocode (1995) and one 
in which the pressure at A is held constant from 0° to 25°; 
these two cases are based on comparison of the Eurocode 
provisions with Taylor (1991). Case A (the Eurocode 
calculation) is necessary in many cases to define maximum 
uplift. Case B is necessaiy to properly define positive 
pressures for some cases , which cannot be isolated with 
current information , and which result in maximum base 
shear. For domes larger than 60 m in diameter the 
designer should consider use of wind-tunnel testing. 
Resonant response is not considered in these provisions. 
Wind-tunnel testing should be used to consider resonant 
response. Local bending moments in the dome shell may be 
larger than predicted by this method due to the difference 
between instantaneous local pressure distributions and 
those predicted by Figure 207 B. 4-2. If the dome is 
supported on vertical walls directly below \ it is appropriate 
to consider the walls as a “ chimney ” using Figure 207D. 5- 
1 . 


Figure 207B.4-3 . The pressure and force coefficient values 
in these tables are unchanged from ANSI A58.1-1972. The 
coefficients specified in these tables are based on wind- 
tunnel tests conducted under conditions of uniform flow 
and low turbulence t and their validity in turbulent 
boundary-layer flows has yet to be completely established. 
Additional pressure coefficients for conditions not 
specified herein may be found in SI A (1956) and ASCE 
(1961). 

207B.4.2 Enclosed and Partially Enclosed Flexible 
Buildings 

Design wind pressures for the MWFRS of flexible 
buildings shall be determined from the following equation: 

p = qGfCp - q t (GC pl ) (N/m 2 ) (207B.4-2) 

where q, q h C p , and (GC pi ) are as defined in Section 
207B.4.1 and Gf (gust-effect factor) is determined in 
accordance with Section 207A.9.5. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-71 


?07B.4.3 Open Buildings with Monoslope, Pitched, or 
Troughed Free Roofs 

The net design pressure for the MWFRS of open buildings 
with monoslope, pitched, or troughed roofs shall be 
determined by the following equation: 

P = <!hGC N (N/m 2 ) (207B.4-3) 

where 

|. q h “ velocity pressure evaluated at mean roof 
height h using the exposure as defined in 
Section 207A.7.3 that results in the highest 
wind loads for any wind direction at the 
site 

G ~ gust-effect factor from Section 207A.9 
C N = net pressure coefficient determined from 
Figures 207 B. 4-4 through 207 B, 4-7 

Net pressure coefficients, C N , include contributions from 
top and bottom surfaces. Ail load cases shown for each roof 
angle shall be investigated. Plus and minus signs signify 
pressure acting toward and away from the top surface of 
the roof, respectively. 

For free roofs with an angle of plane of roof from 
horizontal 0 less than or equal to 5° and containing fascia 
panels, the fascia panel shall be considered an inverted 
parapet. The contribution of loads on the fascia to the 
MWFRS loads shall be determined using Section 207B.4.5 
with q p equal to q h . 

| Commentary: 

Figures 2078,4-4 through 2078. 4-6 and 207E.8-1 
through 207E.8-3 are presented for wind loads on 
MWFRSs and components and cladding of open 
buildings with roofs as shown, respectively. This work is 
based on the Australian Standard AS 1 170.2-2000, Part 
v2: Wind Actions, with modifications to the MWFRS 
pressure coefficients based on recent studies (Altman 
• | W(id Uematsu and Stathopoulos 2003). 

Two load cases, A and 8, are given in Figures 207B. 4-4 
through 2078.4-6. These pressure distributions provide 
loads that envelop the results from detailed wind-tunnel 
measurements of simultaneous normal forces and 
moments. Application of both load cases is required to 
\ envelop the combinations of maximum normal forces 
and moments that are appropriate for the particular 
l roof shape and blockage configuration. 

■ The roof wind loading on open building roofs is highly 
dependent upon whether goods or materials are stored 


under the roof and restrict the wind flow. Restricting the 
flow can introduce substantial upward acting pressures 
on the bottom surface of the roof thus increasing (hex 
resultant uplift load on the roof. Figures 2078.4-4 
through 2078.4-6 and 207E.8- 1 through 207E.8-3 offer 
the designer two options. Option 1 (clear wind flow) 
implies little (less than 50 percent) or no portion of the 
cross-section below the roof is blocked. Option 2 
(obstructed wind flow) implies that a significant portion 
(more them 75 percent is typically referenced in the 
literature) of the cross-section is blocked by goods or 
materials below the roof Clearly, values would change 
from one set of coefficients to the other following some 
sort of smooth , but as yet unknown, relationship , In 
developing the provisions included in this code , the 
50 percent blockage value was selected for Option 1, 
with the expectation that it represents a somewhat 
conservative transition. If the designer is not clear about 
usage of the space below the roof or if the usage could 
change to restrict free airflow , then design loads for 
both options should be used. 


207R.4.4 Roof Overhangs 

The positive external pressure on the bottom surface of 
windward roof overhangs shall be determined using 
C p ss 0.8 and combined with the top surface pressures 
determined using Figure 207B.4-1. 

207B.4.5 Parapets 

The design wind pressure for the effect of parapets on 
MWFRS of rigid or flexible buildings with flat, gable, or 
hip roofs shall be determined by the following equation: 

P p = <l P (GC pn ) (N/m 2 ) 207B.4-4 

where 

p p = combined net pressure on the parapet due 
to the combination of the net pressures 
from the front and back parapet surfaces. 
Plus (and minus) signs signify net 
pressure acting toward (and away from) 
the front (exterior) side of the parapet 
q p = velocity pressure evaluated at the top of 
the parapet 

combined net pressure coefficient 
-H .5 for windward parapet 
-1.0 for leeward parapet 


(cc p „) 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-72 CHAPTER 2 - Minimum Design Loads 


207B.4.6 Design Wind Load Cases 

The MWFRS of buildings of all heights, whose wind loads 
have been determined under the provisions of this chapter, 
shall be designed for the wind load cases as defined in 
Figure 207B.4-8. 


Exception; 

Buildings meeting the requirements of Section DJ.J of 
Appendix D, ASCE 7-10 need only he designed for Case 1 
and Case 3 of Figure 207 B. 4-8. 

The eccentricity e for rigid structures shall be measured 
from the geometric center of the building face and shall be 
considered for each principal axis (e x ,e Y ). The 
eccentricity e for flexible structures shall be determined 
from the following equation and shall be considered for 
each principal axis ( e x , ey)- 


e Q + l-71/ 2 . 


(g QQ e Q) + (0/t Re /t) 2 


!-• 71I 2 J(g Q Qe Q j + (BnRef) 2 


207 B. 4-5 


where 

e Q = eccentricity e as determined for rigid 
structures in Figure 207B.4-S 
e R = distance between the elastic shear center 
and center of mass of each floor 
h* g <?7 (?> and R shall be as defined in Section 
207A.9 


The sign of the eccentricity e shall be plus or minus, 
whichever causes the more severe load effect. 


Commentary: 


Wind tunnel research (Isyumov 1983, Boggs et ai 2000 \ 
kyumov and Case 2000, and Xie and Irwin 2000) has 
shown that torsional load is caused by non-uniform 
pressure on the different faces of the building from wind 
flow around the building , interference effects of nearby 
buildings and terrain , and by dynamic effects on more 
flexible buildings . Load Cases 2 and 4 in Figure 207 B. 4-8 
specifies the torsional loading to 15 percent eccentricity 
under 75 percent of the maximum wind shear for Load 
Case 2. Although this is more in line with wind tunnel 
experience on square and rectangular buildings with 
aspect ratios up to about 2.5, it may not cover all cases, 
even for symmetric and common building shapes where 
larger torsions have been observed. For example , wind 
tunnel studies often show an eccentricity of 5 percent or 


more under full (not reduced) base shear. The designer 
may wish to apply this level of eccentricity at full wind 
loading for certain more critical buildings even though it 
is not required by the code. The present more moderate 
torsional load requirements can in part be justified by the 
fact that the design wind forces tend to be upper-bound for 
most common building shapes . 

In buildings with some structural systems, more severe 
loading can occur when the resultant wind load acts 
diagonally to the building. To account for this effect and 
the fact that many buildings exhibit maximum response in 
the across-wind direction (the standard currently has no 
analytical procedure for this case), a structure should be 
capable of resisting 75 percent of the design wind load 
applied simultaneously along each principal axis as 
required by Case 3 in Figure 2Q7B.4-S. 

For flexible buildings, dynamic effects can increase 
torsional loading . Additional torsional loading can occur 
because of eccentricity between the elastic shear center 
and the center of mass at each level of the structure. 
Equation 207B.4-5 accounts for this effect. 

It is important to note that significant torsion can occur on 
low-rise buildings also (Isyumov and Case 2000) and [ 
therefore , the wind loading requirements of Section 
2 07 B. 4. 6 are now applicable to buildings of all heights . 

,4s discussed in Section 207 F, the wind tunnel procedure 
should always be considered for buildings with unusual 
shapes , rectangular buildings with larger aspect ratios, 
and dynamically sensitive buildings . The effects of torsion 
can more accurately be determined for these cases and for 
the more normal building shapes using the wind tunnel 
procedure. 

207BA7 Minimum Design Wind Loads 

The wind load to be used in the design of the MWFRS for 
an enclosed or partially enclosed building shall not be less 
than 0.77 kN/m 2 multiplied by the wall area of the building 
and 0.38 kN/m 2 multiplied by the roof area of the building 
projected onto a vertical plane normal to the assumed wind 
direction. Wall and roof loads shall be applied 
simultaneously. The design wind force for open buildings 
shall be not less than 0.77 kN/m 2 multiplied by the area Af. 

Commentaiy: 

This section specifies a minimum wind load to be applied 
horizontally on the entire vertical projection of the building 
as shown in Figure C207B.4-L This load case is to be 
applied as a separate load case in addition to the normal 
load cases specified in other portions of this chapter . 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



mi 





2-74 CHAPTER 2 - Minimum Design Loads 



Wall Pressure Coefficients, C p 


Surface 

L/B 


Use With 

Windward Wall 

All values 

0.8 

Qz 


0-1 

-0.5 


Leeward Wall 

2 

-0.3 

<ih 


> 4 

-0.2 

Side Wall 

All values 

-0.7 

qi, 


Roof Pressure Coefficients, for use with q h 


Wind 

Direction 

Windward 

Leeward 

Angie, 9 (degrees) 

Angie, 0 (degrees) 

h/L 

10 

15 

20 

25 

30 

35 

45 

>60 

10 

15 

> 20 

Normal 

to 

Ridge 
for 6 > 
10° 

<0.25 

-0.7 

-0.18 

-0.5 

0.0* 

-0.3 

0.2 

-0.2 

0.3 

P © 

o P 

0.4 

0.010 

-0.3 

-0.5 

-0.6 

0.5 

-0.9 

-0.18 

-0.7 

-0.18 

-0.4 

0.0* 

-0.3 

0.2 

-0.2 

0.2 

-0.2 

0.3 

0.0* 

0.4 

0.010 

-0.5 

-0.5 

-0.6 

>10 

-1.3** 

-0.18 

-1.0 

-0.18 

-0.7 

-0.18 

-0.5 

0.0* 

-0.3 

0.2 

-0.2 

0.2 

0.0* 

0.3 

0.010 

-0.7 

-0.6 

-0.6 

Normal 

to 

Ridge 
for 6 < 
10 ° and 
Parallel 
to ridge 
for all 9 

<0.5 

Horizontal distance from 
windward edge 


*Value is provided for interpolation purposes 

**Value can be reduced linearly with area over which 
it is applicable as follows 

Oto/t/2 

-0.9, -0.18 

h/2 to h 

-0.9, -0.18 

h to 2 h 

-0.5, -0.18 

> 2h 

-0.3, -0.1 8 

>1.0 

0 to h/2 

-1.3**, -0.18 

Area (m 2 ) 

Reduction Factor 

< 9.3 m 2 

1.0 

> h/2 

-0.7, -0.18 

23.2 m 2 

0.9 

> 92.9 m 2 

0.8 


Notes: 

1. 

2. 


3. 


4 . 

5. 

6. 
1 . 


8 . 


9. 


10. For roof slopes greater than 80°, use C„ = 0.8 


Tift 




Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

Linear interpolation is permitted for values of L/B , h/L and 9 other than shown. Interpolation shall only be carried out 
between values of the same sign. Where no value of the same sign is given, assume 0.0 for interpolation purposes. 

Where two values of C p are listed, this indicates that the windward roof slope is subjected to either positive or negative 
pressures and the roof structure shall be designed for both conditions. Interpolation for intermediate ratios of h/L in this 
case shall only be carried out between C p values of like sign. 

For monoslope roofs, entire roof surface is either a windward or leeward surface. 

For flexible buildings use appropriate Gy as determined by Section 207B.9.4. 

Refer to Figure 207B.4-2 for domes and Figure 207B.4-3 for arched roofs. 

Notation: 

B = horizontal dimension of building, m, measured normal to wind direction. 

L = horizontal dimension of building, m, measured parallel to wind direction. 

h = mean roof height in meters, except that eave height shall be used for 6 < 10° 
z = height above ground, m 

G “ gust effect factor. 

q zt Rii = velocity pressure, (N/m 2 ), evaluated at respective height. 

9 - Angle of plane of roof from horizontal, ° 

For mansard roofs, the top horizontal surface and leeward inclined surface shall be treated as leeward surfaces from the 
table. 

Except for MWFRS at the roof consisting of moment resisting frames, the total horizontal shear shall not be less than that 
determined by neglecting wind forces on roof surfaces. 


| 




1 






Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2~75 



“•'(Tv 



A(h g /D> 1.0) 


(K d /D = 0) 


(fi D id 2 0.5) 


B{hp/D = 0) 

B {h g /D £ 0,5) 


0 0.1 0.2 0.3 0.4 0.5 

Ratio of Rise to Diameter, f/D 

External Pressure Coefficients for Domes with a Circular Base 
(Adapted from Eurocode, 1995) 


Notes; 


1. Two load cases shall be considered: 

Case A: C p values between A and B and between B and C shall be determined by linear interpolation along arcs on the dome parallel to the wind 

direction; 

Case B: C v shall be the constant value of A for 0 < 25°, and shall be determined by linear interpolation from 25° to B and from B to C. 

2. Values denote C p to be used with q^hD+f) where hD + / is the height at the top of the dome. 

3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

4. C p is constant on the dome surface for arcs of circles perpendicular to the wind direction; for example, the arc passing through B-B-B and all arcs parallel 
to B-B-B. 

5. For values of hD/D between those listed on the graph curves, linear interpolation shall be permitted. 

6. 0 — 0° on dome spring line, 0 — 90° at dome center top point, f is measured from spring line to top. 

7. The total horizontal shear shall not be less than that determined by neglecting wind forces on roof surfaces. 

8. For f/D values less than 0.05, use Figure 207B.4-1 . 

Figure 207B.4-2 

External Pressure Coefficients, C py Domed Roofs Enclosed, Partially Enclosed Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 



2-76 CHAPTER 2 - Minimum Design Loads 


Conditions 

Rise-to-span 

C P 


ratio, r 

Windward 

Center 

Leeward 



quarter 

half 

quarter 

Roof on elevated 

0 < r < 0.2 

-0.9 

-0.7-r 

-0.5 

structure 

0.2 < r < 0.3 * 

1.5r - 0.3 

1 

0 
Lq 

1 

-0.5 


0.3 < r < 0.6 

2.75 r - 0.7 

-0.7-r 

-0.5 

Roof springing from 
ground level 

0 < r < 0.6 

1.4r 

-0.7-r 

-0.5 


HVhen the rise-to-span ratio is 0. 2 < r < 0. 3, alternate coefficients given by 6r - 2. 1 shall also be used for 
the windward quarter 
Notes: 

1 . Values listed are for the determination of average loads on main wind force resisting systems. 

2. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

3. For wind directed parallel to the axis of the arch, use pressure coefficients from Figure 207B.4-1 with wind directed parallel to ridge. 

4. For components and cladding: (i) At roof perimeter, use the external pressure coefficients in Figure 207E.4-2A, B and C with 0 based on spring-line 
slope and (2) for remaining roof areas, use external pressure coefficients of this table multiplied by 0.87. 

Figure 207B.4-3 

External Pressure Coefficients, C p , Arched Roofs, 0.25 < h/L < 1.0 
Enclosed, Partially Enclosed Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAP I ER 2 - Minimum Design Loads 




1 

■ 


SI 


i 

l 

1 


f 


1 



■ 

1 




| 7.5° 

■ife 

| 


22.5° 


j7. 5° 


45 ° 


Wind Direction, y = 0° 

Clear Wind Flow I Obstructed Wind 



Wind Direction 


Clear Wind Flow Obstructed Wind 

F 

^nw Cnl 


: 2 - 


5 Chw ar >d C Nl denote net pressures (contributions from top and bottom surfaces) for windward and leeward half of roof surfaces, respectively. 

Clear wind flow denotes relatively unobstructed wind flow with blockage less than or equal to 50%. Obstructed wind flow denotes objects below roof 
inhibiting wind flow (> 50% blockage). 

f For values of 0 between 7.5° and 45°, linear interpolation is permitted. For values of 0 less than 7.5°, use load coefficients for 0°. 

4 Plus and minus signs signify pressures acting towards and away from the top roof surface, respectively. 

All load cases shown for each roof angle shall be investigated. 

Notation: 

L ~ horizontal dimension of roof, measured in the along wind direction, m 
h = mean roof height, m 

6 Y “ direction of wind, ° 

0 = angle of plane of roof from horizontal, ° 

Figure 207B.4-4 

Net Pressure Coefficient, C N Monoslope Free Roofs 0 < 45°, y “ 0°, 180° 
tj 0.25 < h/L < 1.0 Open Buildings 





National Structural Code of the Philippines Volume I, 7th Edition, 2015 



















2-78 


CHAPTER 2 - Minimum Design Loads 



Roof 

Angle 

9 

Load 

Case 

Wind Direction, r = 0°, 180° 

Clear Wind Flow 

Obstructed Wind Flow 

C NW 

Cnl 

C NW 

C NL 

7. 5° 

A 

1.1 

-0.3 

-1.6 

-1 

B 

0.2 

-1.2 

-0.9 

-1.7 

15° 

A 

LI 

-0.4 

-1.2 

-1 

B 

0.1 

-1.1 

-0.6 

-1.6 

22.5° 

A 

1.1 

0.1 

-1.2 

“1.2 

B 

-0.1 

-0.8 

-0.8 

-1.7 

30° 

A 

1.3 

0.3 

-0.7 

-0.7 

B 

-0.1 

-0.9 

-0.2 

-1.1 

37.5° 

A 

1.3 

0.6 

-0.6 

-0.6 

B 

-0.2 

-0.6 

-0.3 

-0.9 

45° 

A 

1.1 

0.9 

-0.5 

-0.5 

B 

-0.3 

-0.5 

-0.3 

-0.7 


Notes: 

1. C mv and C NL denote net pressures (contributions from top and bottom surfaces) for windward and leeward half of roof surfaces, respectively. 

2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or equal to S0%. Obstructed wind flow denotes objects below root 
inhibiting wind flow (> 50% blockage). 

3. For values of 9 between 7.5° and 45°, linear interpolation is permitted. For values of 9 less than 7.5°, use monosiope roof load coeffic.ents. 

4. Plus and minus signs signify pressures acting towards and away from the top roof surface, respectively. 

5. All load cases shown for each roof angle shall be investigated. 


6. Notation: 

L 

= horizontal dimension of roof, measured in the along wind direction, m 

h 

= mean roof height, m 

y 

= direction of wind, ° 

e 

= angle of plane of roof from horizontal , ° 


Figure 207B.4-5 

Net Pressure Coefficient, C N Pitched Free Roofs 6 < 45°, y = 0°, 180° 
0.25 < h/L < 1.0 Open Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-79 



Roof 


Wind Direction, y = 0 °, 180 ° 

Angle 

Load 

Clear Wind Flow 

Obstructed Wind Flow 

8 

Case 

Cnw 

Cnl 

C NW 

Cnl 

7. 5 ° 

A 

-i.i 

0.3 

-1.6 

-0.5 

B 

-0.2 

1.2 

-0.9 

-0.8 

15 ° 

A 

-1.1 

0.4 

-1.2 

-0.5 

B 

0.1 

1.1 

-0.6 

-0.8 

22 . 5 ° 

A 

-1.1 

-0.1 

-1.2 

-0.6 

B 

-0.1 

0.8 

-0.8 

-0.8 

30 ° 

A 

-1.3 

-0.3 

-1.4 

-0.4 

B 

-0.1 

0.9 

-0.2 

-0.5 

37. 5° 

A 

-1.3 

-0.6 

-1.4 

-0.3 

B 

0.2 

0.6 

-0.3 

-0.4 

45 ° 

A 

-1.1 

-0.9 

-1.2 

-0.3 

B 

0.3 

0.5 

-0.3 

-0.4 


:||jv Notes: 

§8| l . C NW and C NL denote net pressures (contributions from top and bottom surfaces) lor windward and leeward half of roof surfaces, respectively. 

2. Clear wind flow denotes relatively unobstructed wind How with blockage less than or equal to 50 %. Obstructed wind flow denotes objects below root 
Jiff : inhibiting wind flow (> 50% blockage). 

f8J: 3. For values of 6 between 7.5° and 45°, linear interpolation is permitted. For values of 0 less than 7.5°, use monosiopc roof load coefficients, 

jjpj; 4. Plus and minus signs signify pressures acting towards and away from the top roof surface, respectively. 

§fe 5. All load cases shown for each roof angle shall be investigated. 

Iplg 6. Notation: 

L " horizontal dimension of roof, measured in the along wind direction, m 

h - mean roof height, m 

P§ g, y - direction of wind, ° 

& - angle of plane of roof from horizontal, ° 

jjf' Figure 207B.4-6 

Net Pressure Coefficient, C N Troughed Free Roofs 8 < 45°, y = 0°, 180° 

0.25 < h/L < 1.0 Open Buildings 





National Structural Code of the Philippines Volume I, 7th Edition, 2015 



2-80 CHAPTER 2 - Minimum Design Loads 



Horizontal 

Distance 

from 

Windward 

Edge 

Roof Angle 

0 

Load Case 

Clear Wind 
Flow 

Obstructed 
Wind Flow 

C NW 

Cni. 

< h 

All Shapes 

A 

-0.8 

1.2 

e < 45° 

B 

0.8 

0.5 

> h, < 2h 

All Shapes 

A 

-0.6 

-0.9 

9 < 45° 

B 

0.5 

0.5 

> 2h 

All Shapes 

A 

-0.3 

-0.6 

6 <45° 

B 

0.3 

0.3 


Notes: 


1 . CN denotes net pressures (contributions from top and bottom surfaces). 

2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or equal to 50%. Obstructed wind flow denotes objects below roof 
inhibiting wind flow {> 50% blockage). 

3. Plus and minus signs signify pressures acting towards and away from the top roof surface, respectively. 

4. All load cases shown for each roof angle shall be investigated. 

5. For monoslope roofs with theta less than 5 degrees, C N values shown apply also for cases where gamma “ 0 degrees and 0.05 less than or equal to h/ 1 
less than or equal to 0.25. See Figure 207B.4-4 for other h/L values. 

6. Notation: 

L = horizontal dimension of roof, measured in the along wind direction, m 

h = mean roof height, m. See Figures 207B.4-4, 207B.4-5 or 207B.4-6 for a graphical depiction of this dimension. 

y = direction of wind, ° 

d = angle of plane of roof from horizontal, ° 

Figure 207B.4-7 

Net Pressure Coefficient, C N Free Roofs 6 < 45°, y = 90°, 270° 

0.25 < h/L < 1.0 Open Buildings 


| 












Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-81 


t’m 


?LX 

CASE 1 


— T 

t) 

<»» 

— - 

My 

_ 


&?5P mC 




111 


J 1 I 


Pwr 


r lY 


^ ZJL ^ 

TT 

H | 


£) 

M'i 

r 

LIT 

ii 

i! 




®.75Piy 


0*7$ P pyy 


& 7$ P f%Hj£ 





0,563 P yyy 

, 1, 




1 4 1 1 1 1 i 


* 


t) 



n 

My 

— 

6.5*3 PffX 5 

hhbhw 



0.563 P&y 


M T — * 0.75 (P iyj^P i$)Bx £% Afj — 0. 75 6? y A/y — 0,505 (P wx^Pij^Px ^ 0*505 ^ ^ 

ej = £ 0J5 i?r er = ^ 0,/5 By ex = i 0./5 j?v = i 0./5 By 


CASE 2 


CASE 4 


Case 1: Full design wind pressure acting on the projected area perpendicular to each principal axis of the structure, considered 
separately along each principal axis. 

Case 2: Three quarters of the design wind pressure acting on the projected area perpendicular to each principal axis of the 
structure in conjunction with a torsional moment as shown, considered separately for each principal axis. 

Case 3: Wind loading as defined in Case 1, but considered to act simultaneously at 75% of the specified value. 

Case 4: Wind loading as defined in Case 2, but considered to act simultaneously at 75% of the specified value. 

Nolcs: 

1. Design wind pressures for windward and leeward faces shall be determined in accordance with the provisions of 207BA1 and 207B.4.2 as applicable 
for building of all heights. 

2. Diagrams show plan views of building. 

3. Notation: 

Pwx’Pwy = Windward face design pressure acting in the x, y principal axis, respectively. 

Plx^ly ” Leeward face design pressure acting in the x, y principal axis, respectively. 
e{e x , e Y ) “ Eccentricity for the x, y principal axis of the structure, respectively. 

M r - Torsional moment per unit height acting about a vertical axis of the building. 

Figure 207B.4-8 

Design Wind Load Cases All Heights 


National Structural Code of the Philippines Volume J, 7th Edition, 2015 






2-82 CHAPTER 2 - Minimum Design Loads 


Part 2: Enclosed Simple Diaphragm Buildings with 
h = 48 m 

This section has been added to ASCE 7-10 to cover the 
common practical cases of enclosed simple diaphragm 
buildings up to height h = 48 m. Two classes of buildings 
are covered by this method. Class l buildings have h < 
18 in with plan aspect ratios L/B between 0.2 and 5.0. 
Cases A through F are described in Appendix D, ASCE 7- 
10 to allow the designer to establish the lines of resistance 
of the MWFRS in each direction so that the torsional load 
cases of Figure 207B.4-S need not be considered. Class 2 
buildings have 18 m <h< 48 m with plan aspect ratios 
of L/B between 0.5 and 2.0. Cases A through E of 
Appendix D, ASCE 7-10 are described to allow the 
designer to establish the lines of resistance of the MWFRS 
so that the torsional load cases of Figure 207 B. 4-8 need 
not be considered. 

For the type of buildings covered in this method the 
internal building pressure cancels out and need not be 
considered for the design of the MWFRS. Design net wind 
pressures for roofs and walls are tabulated directly in 
Tables 207 B. 6-1 and 207 B. 6-2 using the Directional 
Procedure as described in Part 1. Guidelines for 
determining the exterior pressures on windward, leeward, 
and side walls are provided in footnotes to Table 207 B. 6- 
L 

The requirements in Class 2 buildings for natural building 
frequency (7 5 /ft) and structural damping (/? - 
1.5% critical) are necessary to ensure that the Gust Effect 
Factor, Gp which has been calculated and built into the 
design procedure, is consistent with the tabulated 
pressures. The frequency of75/h represents a reasonable 
lower bound to values found in practice. If calculated 
frequencies are found to be lower , then consideration 
should be given to stiffening the building. A structural 
damping value of 1.5 %, applicable at the ultimate wind 
speeds as defined in the new wind speed maps, is 
conservative for most common building types and is 
consistent with a damping value of 1% for the ultimate 
wind speeds divided by 1.6 as contained in the NSCP 2010 
(ASCE 7-05) wind speed map. Because Class l buildings 
are limited to h < 18 in, the building can be assumed to 
be rigid as defined in the glossary , and the Gust Effect 
Factor can be assumed to be 0.85. For this class of 
buildings frequency and damping need not be considered. 


207B.5 General Requirements 
207B.5.1 Design Procedure 

The procedure specified herein applies to the determination 
of MWFRS wind loads of enclosed simple diaphragm 
buildings, as defined in Section 207A.2, with a mean roof 
height h < 48 m. The steps required for the determination 
of MWFRS wind loads on enclosed simple diaphragm 
buildings are shown in Table 207B.5-1. 


User Note: 

Part 2 of Section 207 B is a simplified method for 
determining the wind pressures for the MWFRS of 
enclosed ' simple diaphragm buildings whose height 
h is < 4 m. The wind pressures are obtained directly 
from a table. The building may be of any general plan 
shape and roof geometry that matches the specified 
figures. This method is a simplification of the traditional 
“ all heights ” method (Directional Procedure) 
contained in Part l of Section 207 B. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-83 




Table 207B.5-1 

Steps to Determine MWFRS Wind 
Loads Enclosed Simple Diaphragm Buildings 
( ft <48 m) 


Step I : 
Step 2: 

:: Step 3: 


Determine risk category of building or other 
structure, see Table 103-1 

Determine the basic wind speed, V , for the 
applicable risk category, see Figure 207A.5- 
1A, BorC 

Determine wind load parameters: 

> Wind directionality factor, K d , see 
Section 207A.6 and Table 207A.6-1 

> Exposure category B, C or D, see 
Section 207A.7 

> Topographic factor, I( zt , see 
Section 207A.8 and Figure 207A.8-1 


Enclosure classification, 
Section 207A.I0 


see 


Step 4: 

Step 5: 
Step 6: 

Step 7: 


Enter table to determine net pressures on 
walls at top and base of building respectively, 
Vh ,p G , Table 207B.6-1 

Enter table to determine net roof pressures. 
Table 207B.6-2 

Determine topographic factor, K zt , and apply 
factor to wall and roof pressures (if 
applicable), see Section 207A.8 

Apply loads to walls and roofs 
simultaneously. 


207B.5.2 Conditions 

;fn addition to the requirements in Section 207B.1.2, a 
building whose design wind loads are determined in 
accordance with this section shall meet all of the following 
conditions for either a Class 1 or Class 2 building (see 
Figure 207B.5-1): 

Class 1 Buildings: 

F The building shall be an enclosed simple diaphragm 
building as defined in Section 207A.2. 

2. The building shall have a mean roof height ft < 1 8 m. 

The ratio of L/B shall not be less than 0.2 nor more 
than 5.0 (0. 2 < L/B < 5. 0). 


4. The topographic effect factor K zt =s 1. 0 or the wind 
pressures determined from this section shall be 
multiplied by K zt at each height z as determined from 
Section 207A.8. It shall be permitted to use one value 
of K zt for the building calculated at 0.33ft. 
Alternatively it shall be permitted to enter the pressure 
table with a wind velocity equal to V<jK zt where K zt 
is determined at a height of 0. 33ft. 


Class 2 Buildings: 

1. The building shall be an enclosed simple diaphragm 
building as defined in Section 207A.2. 

2. The building shall have a mean roof height 18 m 
(18 m < ft < 48 m). 

3. The ratio of L/B shall not be less than 0.5 nor more 
than 2.0 (0.5 < L/B < 2.0). 

4. The fundamental natural frequency (Hertz) of the 
building shall not be less 75/ft where ft is in meters. 

5. The topographic effect factor I( zt = 10 or the wind 
pressures determined from this section shall be 
multiplied by K zt at each height z as determined from 
Section 207 A. 8. It shall be permitted to use one value 
of K zt for the building calculated at 0.33 ft. 
Alternatively it shall be permitted to enter the pressure 
table with a wind velocity equal to V^K zt where K zt 
is determined at a height of 0. 33ft. 

207B.5.3 Wind Load Parameters Specified in Section 
207A 

Refer to Section 207A for determination of Basic Wind 
Speed V (Section 207A.5) and exposure category 
(Section 207A.7) and topographic factor K zt (Section 
207A.8). 

207B.5.4 Diaphragm Flexibility 

The design procedure specified herein applies to buildings 
having either rigid or flexible diaphragms. The structural 
analysis shall consider the relative stiffness of diaphragms 
and the vertical elements of the MWFRS. 

Diaphragms constructed of wood panels can be idealized 
as flexible. Diaphragms constructed of untopped metal 
decks, concrete filled metal decks, and concrete slabs, each 
having a span-to-depth ratio of 2 or less, are permitted to 
be idealized as rigid for consideration of wind loading. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-84 CHAPTER 2 - Minimum Design Loads 


207B.6 Wind Loads— Main Wind Force-Resisting 
System 

207B.6.1 Wall and Roof Surfaces — Class 1 and 2 
Buildings 

Net wind pressures for the walls and roof surfaces shall be 
determined from Tables 207B.6-1 and 207B.6-2, 
respectively, for the applicable exposure category as 
determined by Section 207A.7. 

For Class 1 building with L/B values less than 0.5, use 
wind pressures tabulated for L/B — 0.5. For Class 1 
building with L/B values greater than 2.0, use wind 
pressures tabulated for L/B = 2.0. 

Net wall pressures shall be applied to the projected area of 
the building walls in the direction of the wind, and exterior 
side wall pressures shall be applied to the projected area of 
the building walls normal to the direction of the wind 
acting outward according to Note 3 of Table 207B.6-1, 
simultaneously with the roof pressures from Table 207B.6- 
2 as shown in Figure 207B.6-I . 

Where two load cases are shown in the table of roof 
pressures, the effects of each load case shall be investigated 
separately. The MWFRS in each direction shall be 
designed for the wind load cases as defined in Figure 
207B.4-S. 

Exception: 

The torsional load cases in Figure 20? B 4-8 (Case 2 and 
Case 4) need not he considered for buildings which meet 
the requirements of Appendix 0. ASCE 7-10, 

Commentary: 

Wall and roof net pressures are shown in Tables 207 8. 6-1 
and 2078,6-2 and are calculated using the external 
pressure coefficients in Figure 207 B, 4-1. Along wind net 
wall pressures are applied to the projected area of the 
building walls in the direction of the wind, and exterior 
sidewall pressures are applied to the projected area of the 
building walls normal to the direction of the wind acting 
outward [ simultaneously with the roof pressures from 
Table 2078,6-2 . Distribution of the net wall pressures 
between windward and leeward wall surfaces is defined in 
Note 4 of Table 2078,6-1. The magnitude of exterior 
sidewall pressure is determined from Note 2 of Table 
207B. 6-1. It is to be noted that all tabulated pressures are 
defined without consideration of internal pressures 
because internal pressures cancel out when considering 
the net effect on the MWFRS of simple diaphragm 
buildings . Where the net wind pressure on any individual 


wall surface is required, internal pressure must he , |§f 
included as defined in Part 1 of Section 207 B. 

The distribution of wall pressures between windward and ffj 
leeward wall surfaces is useful for the design of floor and | 
roof diaphragm elements like drag strut collector beams, JJJ 
as well as for MWFRS wall elements. The values defined in |f 
Note 4 of Table 2078.6-1 are obtained as follows: The J§f 
external pressure coefficient for all windward walls is ;§§ 
C p = 0.8 for all L/B values . The leeward wall C p value is Jj 
(-0.5) for L/B values from 0.5 to 1.0 and is (-0.3) for L/B 
= 2. 0. Noting that the leeward wall pressure is constant for W 
the full height of the building, the leeward wall pressure jj| 
can be calculated as a percentage of the Pi t value in the. Jjj 
table. The percentage is 0. 5/(0. 8 + 0.5) x 100 - 38% for :j§f 
L/B = 0.5 to 1.0. The percentage is 0.37(0.8+0.3) x 1 00 =» jj 
27% for L/B = 2.0 . Interpolation between these two fp 
percentages can be used for L/B ratios between 1.0 ami |j 
2.0. The windward wall pressure is then calculated as the ; Iff 
difference between the total net pressure from the table \ §J, 
using the p h and p 0 values and the constant leeward wall |j 
pressure. 

Sidewall pressures can be calculated in a similar manned ||j 
to the windward and leeward wall pressures by taking a > 
percentage of the net wall pressures. The C p value fan j§| 
sidewalls is (-0.7). Thus , for L/B = 0.5 to 1.0, the |j 
percentage is 0. 7/(0. S + 0.5) x 100 - 54%. For L/B = 2, Or :|J|L 
the percentage is 0. 7/(0. 8 + 0.3) * 100 ~ 64%. Note that ||i 
the sidewall pressures are constant up the full height of the |j 
building. 

The pressures tabulated for this method are based on jjj. 
simplifying conservative assumptions made to the different jjj 
pressure coefficient ( GC p ) cases tabulated in Figure |j| 
207 B. 4- 1, which is the basis for the traditional all heights Jjti 
building procedure (defined as the Directional Procedure ||| 
in this code) that has been a part of the standard since ;jj| 
1972. The external pressure coefficients C p for roofs have ^ 
been multiplied by 0.85 , a reasonable gust effect factor for ^ 
most common roof framing, and then combined with an ij 
internal pressure coefficient for enclosed buildings (plus or jjg 
minus 0. 18) to obtain a net pressure coefficient to serve as Jjj 
the basis for pressure calculation. The linear wall pressure |g 
diagram has been conceived so that the applied pressures. Iff 
from the table produce the same overturning moment as the Jj| 
more exact pressures from Part 1 of Section 207 B. For jjj 
determination of the wall pressures tabulated, the actual gjj 
gust effect factor has been calculated from Equation 
207 A. 9-10 based on building height, wind speed , exposure , jjf 
frequency , and the assumed damping value. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-85 



207B.6.2 Parapets 

The effect of horizontal wind loads applied to all vertical 
surfaces of roof parapets for the design of the MWFRS 
shall be based on the application of an additional net 
horizontal wind pressure applied to the projected area of 
the parapet surface equal to 2.25 times the wall pressures 
tabulated in Table 207B.6-1 for L/B = 1.0. The net 
pressure specified accounts for both the windward and 
leeward parapet loading on both the windward and leeward 
building surface. The parapet pressure shall be applied 
simultaneously with the specified wall and roof pressures 
shown in the table as shown in Figure 207B.6-2. The height 
h used to enter Table 207 B. 6-1 to determine the parapet 
pressure shall be the height to the top of the parapet as 
shown in Figure 207B.6-2 (use h — lip). 


Commentary: 


ttr 


mm 


The effect of parapet loading on the MWFRS is specified in 
Section 207 BA. 5 of Part 1. The net pressure coefficient for 
the windward parapet is +1.5 and for the leeward parapet 
is ~~ l .0. The combined effect of both produces a net 
coefficient of +2.5 applied to the windward surface to 
Account for the cumulative effect on the MWFRS in a 
Simple diaphragm building . This pressure coefficient 
compares to a net pressure coefficient of 1.3 Gf for the 
tabulated horizontal wall pressure p fl at the top of the 
building. Assuming a lower-bound gust factor 
Gf = 0. 85, the ratio of the parapet pressure to the wall 
pressure is 2.57(0.85 *1.3) - 2.25. Thus . a value of 2.25 is 
assumed as a reasonable constant to apply to the tabulated 
wall pressure p h to account for the additional parapet 
loading on the MWFRS. 

207B.6.3 Roof Overhangs 






The effect of vertical wind loads on any roof overhangs 
| shall be based on the application of a positive wind 
pressure on the underside of the windward overhang equal 
to 75% of the roof edge pressure from Table 207B.6-2 for 
Zone 1 or Zone 3 as applicable. This pressure shall be 
applied to the windward roof overhang only and shall be 
applied simultaneously with other tabulated wall and roof 
pressures as shown in Figure 207B.6-3. 


Commentary: 

The effect of vertical wind loading on a windward roof 
overhang is specified in Section 207 BA. 4 of Part 1. A 
positive pressure coefficient of +0.8 is specified. This 
compares to a net pressure coefficient tabulated for the 
windward edge zone 3 of —1.06 (derived from 
0.85 x -1.3 x 0.8 - 0.18). The 0.85 factor represents the 
gust factor G, the 0.8 multiplier accounts for the effective 
wind area reduction to the 1.3 value of C p specified in 
Figure 207 BA-1 of Part 1, and the - 0.18 is the internal 
pressure contribution. The ratio of coefficients is 0.8/1.06 
- 0.755. Thus , a multiplier of 0.75 on the tabulated 
pressure for zone 3 in Table 207 B. 6-2 is specified. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-86 


CHAPTER 2 - Minimum Design Loads 


0.21 < B < 5L 






f 

L 

1 


CLASS 1 BUILDING 



O 5L < B < 2 L 




PLAN 



CLASS 2 BUILDING 


ELEVATION 


Note: Roof form may be flat, gable, mansard or hip 

Figure 207B.5-1 

Building Geometry Requirements Building Class, h < 48 m 
Enclosed Simple Diaphragm Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-87 


SEE FIGURE 207B.6-2 FOR 

PARAPET WIND PRESSURES ROOF PRESSURES 



ELEVATION 


Figure 207 B. 6-1 

Application of Wind Pressures Wind Pressures - Walls and Roof, ft < 48 m 
Enclosed Simple Diaphragm Buildings 



Jl 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-88 CHAPTER 2 - Minimum Design Loads 



Figure 20 7 B. 6-2 

Application of Parapet Wind Loads Parapet Wind Loads, h < 48 m 
Enclosed Simple Diaphragm Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 


2-89 



Enclosed Simple Diaphragm Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 



PLAN 


WIND PRESSURE ELEVATION 


Notes to Wall Pressure Table 207B.6-1 : 

1 . From table for each Exposure (B C or D), V, L/B and h, determine p h (top number) and p„ (bottom number) horizontal along-wind net wall pressures 
“ L 't < a {' o“‘P re ” f b ( e . umform over ‘ hc 'I a " surfa / cc acti "S ou t wa rd and shall be taken as 54% of the tabulated p h pressure for 0. 2 < 

n^c! y al °" S 7 ind " et . W f P^^resas shown above to the projected area of the building walls in the direction of the wind and apply external side wall 

Distribution of tabuhmf °ii ^ Wal ' S n ° rm , al ‘° dlrection wind ’ simultaneously with the roof pressures from Table 207B.6-2. 

Distribution of tabu ated net wall pressures between windward and leeward wall faces shall be based on the linear distribution of total net pressure with 

38% ofm'forO T kT/B oSndVvv T T"?' fm™? assumed uniformly distributed over the leeward wall surface acting outward at 
^ \ 11 u ~v l “I 1 ^ J1 ^ ^ /0 °^ /l or ^ ® — 5*0’ Linear interpolation shad be used for 1 0 < L/B <20 The remaininf? net 

^ pre “" re “ ine - ” r “- «— - “'•» r~ » 

Interpolation between values of V, h and L/B is permitted. 

Notation: 


3. 

4. 


L “ building plan dimension parallel to wind direction, m 

B = building plan dimension perpendicular to wind direction, m 

h - mean roof height, m 

Vh>Po ~ along-wind net wall pressure at top and base of building respectively. Pa 

Figure 207B.6-1 

Application of Wall Pressures Wind Pressures - Walls, h < 48 in 
Enclosed Simple Diaphragm Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads , 


Table 207B.6-1 

MWFRS - Part 2: Wind Loads - Walls (kN/nr) 
Exposure B 


V ( kph ) 

150 

200 

250 


iUU 



h ( m ), 
r /r 

0.5 

1 

2 

0.5 

1 

2 

0.5 

1 

2 0.5 

1 2 

0.5 

1 2 


1.24 

1.22 

1.09 

2.39 

2.36 

2.15 

4.03 

3.96 

3.63 6.25 

6.11 5.61 

9.14 

8.90 8.17 

48 

0.83 

0.82 

0.67 

1.61 

1.59 

1.33 

2.72 

2.67 

2.24 4.22 

4.12 3.47 

6.17 

6.00 5.09 


1.20 

1.19 

1.06 

2.31 

2.29 

2.08 

3.88 

3.82 

3.50 6.00 

5.88 5.40 

8.76 

8.57 7.86 

45 

0.82 

0.81 

0.66 

1.58 

1.56 

1.30 

2.65 

2.61 

2.19 4.09 

4.01 3.39 

5.96 

5.81 4.96 


1.16 

1.15 

1.03 

2.23 

2.21 

2.00 

3.73 

3.68 

3.37 5.75 

5.64 5.19 

8.38 

8.17 7.51 

42 

0.79 

0.80 

0.65 

1.54 

1.53 

1.27 

2.57 

2.54 

2.14 3.97 

3.89 3.30 

5.83 

5.64 4.79 


1.13 

1.12 

1.00 

2.14 

2.13 

1.93 

3.57 

3.53 

3.23 5.49 

5.40 4.97 

7.97 

7.82 7.22 

39 

0.78 

0.79 

0.64 

1.50 

1.49 

1.25 

2.50 

2.47 

2.09 3.84 

3.78 3.21 

5.58 

5.47 4.66 


1.08 

1 09 

0.96 

2.06 

2.05 

1.85 

3.42 

3.38 

3.09 5.23 

5.15 4.74 

7.56 

7.43 6.86 

36 

0.77 

0.77 

0.64 

1.46 

1.45 

1.22 

2.42 

2.40 

2.03 3.71 

3.66 3.12 

5.39 

5.27 4.54 ] 


1.04 

1.05 

0.93 

1.98 

1.97 

1.77 

3.26 

3.23 

2.94 4.97 

4.90 4.51 

7.20 

7.05 6.55 

33 

0.76 

0.76 

0.63 

1.43 

1.42 

1.19 

2.35 

2.33 

1.98 3.58 

3.54 3.03 

5.18 

5.10 4.37 


1.01 

1.00 

0.89 

1.90 

1.88 

1.69 

3.10 

3.08 

2.80 4.70 

4.65 4.27 

6.79 

6.64 6.15 

30 

0.73 

0.74 

0.61 

1.39 

1.38 

1.16 

2.27 

2.26 

1.92 3.45 

3.41 2.93 

5.01 

4.86 4.23 

27 

0.97 

0.96 

0.86 

1.85 

1.80 

1.60 

2.94 

2.92 

2.65 4.43 

4.39 4.02 1 

6.51 

6.28 5.72 

0.73 

0.72 

0.60 

1.35 

1.34 

1.13 

2.20 

2.19 

1.86 3.32 

3.28 2.83 

4.75 

4.62 4.08 

24 

0.93 

0.92 

0.81 

1.71 

1.71 

1.52 

2.77 

2.76 

2.49 4.16 

4.13 3.77 

5.93 

5.88 5.41 

0.71 

0.72 

0.60 

1.31 

1.31 

1.10 

2.12 

2.11 

1.80 3.18 

3.16 2.72 

4.53 

4.50 3.88 


0.88 

0.89 

0.77 

1.62 

1.61 

1.43 

2.60 

2.59 

2.33 3.88 

3.86 3.50 

5.52 

5.45 4.97 

21 

0.69 

0.69 

0.57 

1.27 

1.27 

1.07 

2.04 

2.04 

1.74 3.05 

3.03 2.61 

4.35 

4.27 3.71 

18 

0.83 

0.85 

0.73 

1.52 

1.52 

1.34 

2.43 

2.42 

2.16 3.60 

3.58 3.23 

5.07 

5.03 4.59 

0.68 

0.68 

0.55 

1.23 

1.23 

1.03 

1.97 

1.96 

1.67 2.91 

2.90 2.50 

4.06 

4.08 3.55 


0.78 

0.78 

0.69 

1.41 

1.41 

1.24 

2.25 

2.25 

1.99 3.31 

3.30 2.95 

4.60 

4.56 4.13 

15 

0.65 

0.65 

0.56 

1.19 

1.19 

1.00 

1.89 

1.89 

1.61 2.78 

2.77 2.39 

3.89 

3.85 3.34 


0.74 

0.74 

0.63 

1.31 

1.31 

1.14 

’ 2.07 

2.07 

1.82 3.03 

3.03 2.69 

4.20 

4.20 3.77 

!2 

0.65 

0.63 

0.52 

1.15 

1.15 

0.97 

1.82 

1.82 

1.55 2.66 

2.66 2.29 

3.67 

3.69 3.22 


0.67 

0.67 

0.57 

1.19 

1.19 

1.03 

1.88 

1.88 

1 .64 2.74 

2.74 2.40 

’ 3.77 

3.77 3.31 

9 

0.62 

0.62 

0.53 

1.10 

1.10 

0.94 

1.74 

1.74 

1.49 2.53 

2.53 2.19 

3.46 

3.46 3.05 


0.59 

0.59 

0.51 

1.07 

1.07 

0.93 

1.68 

1.68 

1.46 2.43 

2.43 2.12 

3.33 

3.33 2.93 

6 

0.59 

0.59 

0.51 

1.05 

1.05 

0.91 

1.65 

1.65 

1.43 2.39 

2.39 2.08 

3.27 

3.27 2.8' 


0.38 

” 0.38 

0.33 

0.67 

0.67 

0.58 

1.05 

1.05 

0.91 1.51 

1.51 1.33 

2.04 

2.04 1.85 

3 

0.38 

0.38 

0.33 

0.67 

0.67 

0.58 

. 1.05 

1.05 

0.91 1.51 

1.51 1.33 

; 2.04 

2.04 1.81 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-92 CHAPTER 2 - Minimum Design Loads 


Table 207B.6-1 

MWFRS - Part 2: Wind Loads - Walls (IcN/m 2 ) 
Exposure C 


V (kph) 
h (m), 
L/B 


1.58 1.42 

1.16 0.97 

1.55 1.38 

1.16 0.96 

1.51 1.33 

1.13 0.94 


0.5 

1 

2 

0.5 

1 

2 

0.5 

3.10 

3.06 

2.75 

5.21 

5.11 

4.62 

8.04 

2.28 

2.25 

1.89 

3.83 

3.76 

3.19 

5.92 

3.01 

2.97 

2.68 

5.06 

5.04 

4.49 

7.79 

2.24 

2.21 

1.87 

3.75 

3.74 

3.13 

5.78 

2.92 

2.89 

2.60 

4.90 

4.87 

4.36 

7.53 

2.19 

2.17 

1.85 

3.67 

3.65 

3.07 

5.65 


7.85 7.10 

5.77 4.89 

7.61 6.89 

5.65 4,81 

7.37 6.68 

5.53 4.71 



06 

84 


1.01 


.00 1 0.83 


1.96 1.95 


2.34 2.08 3.83 3.81 3.42 5.78 


1.92 1.91 1.63 3.12 


2.24 2.24 1.98 3.63 


2 2.99 2.59 4.53 

3 3.42 3.05 

2.92 I 2.75 I 2.51 




4.82 

4.18 

6.94 

6.88 

4.18 


5.72 

5.19 

8.28 

8.11 

5.19 

4.66 

4.05 

6.72 

6.61 

4.05 



1.86 


2.13 I 2.13 1.88 


2.07 1.81 


2.01 2.01 




3.21 2.85 


2.81 


4.17 


3.01 I 2.99 I 2.63 I 4.41 


3.05 3.77 


4.75 4.25 


4.16 I 3.63_ 
4.39 I 3.90 


6.58 

5.60 

3.92 

7.26 

7.16 

4.58 

7.21 

1.94 

3.77 


0.56 0.56 


0.56 0.56 0.49 


.60 1.60 1.38 

.58 1.58 1.36 

.0! 1.01 0.88 1.59 


2.71 1 2.71 I 2.34 
.51 I 2.87 2.76 2.41 


.38 2.55 

.36 2.49 




3.98 I 3.47 
4.02 1 3.53 



2.25 

3.80 

2.40 

3.65 

2.37 

3.60 

1.38 

2.30 


3.79 3.30 


3.18 



1.0) I 1.01 I 0.88 I 1.59 1.59 1.38 2.30 


QgSEDEIEBHEESIB^I 


2.30 2.00 3.14 
2.30 2.00 3.14 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 















































































































CHAPTER 2 - Minimum Design Loads 2 



Table 207B.6-1 

MWFRS - Part 2: Wind Loads - Walls (kN/m 2 ) 
Exposure D 


3.50 3.45 3.08 5.87 5.75 5.15 9.00 

2.70 2.66 2.25 4.52 4.43 3.76 6.93 

3.42 3.37 3.01 5.72 5.61 5.02 8.76 

2.66 2.62 2.22 4.44 4.36 3.70 6.80 

3.33 3.29 2.94 5.56 5.46 4.89 8.51 

2.61 2.58 2.19 4.36 4.28 3.65 6.66 


5.40 5.31 4.76 I 8.24 


3.24 I 3.21 


2.54 2.16 I 4.27 


3.12 2.78 


\msm 


I 2.52 I 2.49 


1.87 1.61 



1.57 


1.28 I 


1.52 


1.25 1.26 


1.48 1.47 


.25 1.24 


i 06 1 3.03 1 2.70 | 5.05 
2.47 2.45 2.08 4.08 1 4,03 

2.62 4.87 4.82 


59 I 6.52 
62 7.97 

3.52 I 6.37 


7.69 


8.79 7.86 

6.77 5.74 

8.56 7.67 

6.65 5.65 

8.33 7.46 

6.52 5.56 


6.39 5.46 


7.82 7.03 


6.25 5.36 


7.55 I 6.80 



2.41 I 2.40 I 2.05 


2.52 4.68 

2.35 I 2.01 3.88 


2.75 I 2.74 2.43 4,49 

2.31 2.30 1.97 3.78 I 3.75 | 3.24 

64 2.63 2.32 4.28 I 4.26 


4.16 7.08 


5.95 I 5.14 


6.99 6.29 



ii 

98 




K&illB&ui 

QUEUES ^^9 El£3 


5.79 

5.02 

8.35 ! 

8.26 


64 


26 



1.39 


1.19 


1.32 


1.19 1.17 


1.26 1.24 


1.16 1.14 


1.19 1.17 



1.13 

0.96 

1.09 

0.93 

1.09 

0.93 

0.70 

0.60 

0.70 

0.60 


26 I 2.25 1.93 3.67 3.65 

2.52 I 2.52 I 2.22 4.07 4.05 1 3.60 1 6.07 

2.21 I 2.20 | 1.88 3.56 3.54 3.06 5.31 

2.40 2.10 3.85 3.83 3.39 5.70 

2.14 1.84 3.44 3.43 2.97 5.10 


I 2.27 I 2.27 1.97 3.61 3.61 3.16 5.3 


I 2.09 I 2.09 I 1.79 I 3.36 3.32 


I 2.12 I 2.12 1.83 


1.73 


1.97 


1.95 1.95 


6.68 6.01 


5.62 4.89 


I 6.36 I 5.72 


1 5 - 45 1 zJl 

61)3 I 5.40 
5.27 1 4.60 


9.51 

8.60 


7.94 

6.95 




5.67 

5.06 

7.99 

7.98 

7.16 


5.08 4.43 


5.30 

4.69 

7.40 

7.38 


3.20 2.76 I 4,68 

3.09 I 3.09 2.68 4.49 


3.06 3.06 2.65 I 4.45 

1.25 | 1.25 | 1.08 1 1.96 1.96 1.70 2.83 

1.25 1.25 1.08 1.96 1.96 1.70 2.83 


4.88 4.26 


1 490 4,30 

I 4.67 4.07 


4.49 3.91 


3.86 


2.83 2.47 

2.83 2.47 



National Structural Code of the Philippines Volume I, 7th Edition, 2015 

























































































































Notes to Roof Pressure Table 207B.6-2: 

1. From table for Exposure C, V , h and roof slope, determine roof pressure for each roof zone shown in the figures for the applicable roof form. For 
other exposures B or D, multiply pressures from table by appropriate exposure adjustment factor as determined from figure below. 

2. Where two load cases are shown, both load cases shall be investigated. Load case 2 is required to investigate maximum overturning on the building from 
roof pressures shown. 

3. Apply along-wind net wall pressures to the projected area of the building walls in the direction of the wind and apply exterior side wall pressures to the 
projected area of the building walls normal to the direction of the wind acting outward, simultaneously with the roof pressures from Table 207B.6-2. 

4. Where a value of zero is shown in the tables for the fiat roof case, it is provided for the purpose of interpolation. 

5. Interpolation between V> h and roof slope is permitted. 


Figure 207B.6-2 

Application of Roof Pressures Wind Pressures - Roofs, h < 48 m 
Enclosed Simple Diaphragm Buildings 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 










































CHAPTER 2 - Minimum Design Loads 


\ © 

~v©-- 




Flat Roof 
(8 < 10 def$ 



&*> 


Gable Roof 




Hip Roof 





\\0i 



Monoslope 

Roof 


Mansard Roof 


Figure 207B.6-2 

Application of Roof Pressures Wind Pressures - Roofs, h < 48 m 
Enclosed Simple Diaphragm Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 



















CHAP i ER 2 - Minimum Design Loads 


2-97 


Table 207B.6-2 

MWFRS - Part 2: Wind Loads - Roof (kN/m 2 ) 
MWFRS - Roof, V = 300 - 350 kph, h =* 3 - 12 m 
Exposure C 


K (kph) 


300 

350 



E 

E 

Zone 

Zone 

l 

2 

3 

4 

5 

t 

2 

3 

4 

5 


Flat <2:12 {9.46°) 

i 

NA 

NA 

-3.99 

-3.56 

-2.92 

NA 

NA 

-2.38 

-2.12 

-1.74 

2 

NA 

NA 

■HIM 

0.00 

0.00 

NA 

NA 

MM 

BAM 

0.00 

3:12 { 14.0°) 

1 


BSA?»B 


M«« 


m>x%w 

MM 

Bill 

B3I1M 

BWilB 

2 

BAM 

IBfilrM 

MM 

MM 

■♦him 

mxzm 

BAM 

■♦HIM 

■♦HIM 

■(HIM 

4: 12(18.4°) 

1 

-3.22 

-2.60 

-3.99 

-3.56 

-2.92 

-1.91 

■Bl 

mmm 

WfM¥M 

mwLU 

2 

m*¥m 

MW 

■WIM 

mmm 

BAM 

BA<tm 


■♦HIM 

Bihim 

Mum 

5:12(22.6°) 

l 





w>wm 

BMi 

BTCSB 

BAM 

EBB 

mktm 

2 

mwm 

Bl^| 

Bwim 

mmm 

mmm 

mmm 

BfilW 

BAM 

BAM 

BAM' 

6:12(26.6°) 

1 

BAM 


MEM 

MM 

M ?>■ 


MSB 



Bir/B 

2 


■w 

BAfli'B 

hi 

ikmiM 

mmm 


■♦HIM 


■♦HIM 

9:12(36.9°) 

1 

BlfeM 



wkKZM 

B9ESB 

mm 

mmm 



BW 

2 

BUM 

BW 

■♦HIM 

■♦HIM 


MiM 

BAM 

BikM 

B»hhB 

mmm 

12:12(45.0°) 

1 

HAM 

MM 

MUM 

B»T« 



ihpb 

ESEfl 


WKWM 

2 

mwrm 

faiitM 

BAM 

mimm 

■IHIM 


BiKEB 


BAM 

BAMI 


Flat <2:12 (9.46°) 

1 


BM 


BScMtEB 

warnm 

BiftB 



mxnm 

■aw 

2 

BM 

MM 

■♦him 

BAM 

MSESM 




■♦HIM 

■♦him; 

3:12(14.0°) 

1 


■MEHB 

BKl 

tatea 

wswm 





mmm 

2 

0.53 

-0.75 

0.00 

mmm 

0.00 

BAM 

-0.47 


MM 

BAiTiB 

4: 12(18.4°) 

1 

IMBIM 

EEEI 

Mra 

mm&m 

wrxLm 


bum 

BEAM 

mwm 

ESDI 

2 

BUM 

mmm 

BAiliB 

Miim 

mmm 

■hmm 


■♦HIM 

BAM 

■♦HIM 

5:12(22.6°) 

1 

WEIl 

ME EB 

IfclrM 

MM 

mwm 

BW 

BB1 

-2.34 

-2.09 

-1.71 

2 

1.40 

-1.17 

0.00 

BAM 

MAM 

0.68 

-0.73 

0.00 

0.00 

0.00 

6:12(26.6°) 

1 

mwsM 

EBB 

■MM 

BcltEB 

ISMil 


fapM 

BEAM 

MM 

toPrJg 

2 

BUM 

Bllrl 

bam 


BAM 

HiMM 



BAM 

BAM 

9:12(36.9°) 

■m 

Bill 


EBB 


mtm&m 

BArJB 

BfftM 

Btjli 

BEAM 

HfByp 

2 

BBiB 


BAM 


■(HIM 

Bill 

BEES 

BAM 

BAM 

BAM 

12:12(45.0°) 

1 


HI 

El£fl 

BIE1 

Mi 

BflEfiB 

BBl 

BAM 

mxrm 

BW 

2 

1.84 

-1.17 

0.00 

BAM 

BAM 

1.15 

-0.73 

0.00 

0.00 

0.00 


Flat <2:12 (9.46°) 

l 

sn 

B^B 

BBW 

mimm 

b*im 

KW 

BM 

MM 

BAM 

WTM 

2 

MM 

HSEB 


mmm 

mmm 

BTC7AB 

B'?M 

BAM 

BAM 

BAM 

3:12(14.0°) 

l 

wswm 

MiM 


■ffia 

Bi*l 


BW 


BAM 

BEAM 

2 

MEM 

mem 


Milili 

BAM 

■(*»■ 

■♦**■ 

■(HIM 

■♦him 

■♦HIM 

4: 12(18.4°) 

l 

BJW;B 

wrxvm 


BSTM 



MfrKB 

MM 

■w mm 

B^l 

2 

BAM 

BSi I 

BAM 

BAM 

BAM 

BiFM 

BAM 

BAM 

BAM 

Bihim 

5:12(22.6°) 

l 

-2.23 

-2.25 

-3.45 

-3.08 

-2.52 

-1.49 

-1.50 

-2.31 

MM 

-1.69 1 

■H 

1,28 

HiVB 

MM 

0.00 

0.00 

0.24 

-0.72 

0.00 

BAM 

WEESM 

6:12(26.6°) 

1 

-1.79 

-2,25 

-3.45 

-3.08 

-2.52 

-1.20 

-1.50 

-2.31 

-2.06 

-1.69 

2 

1.42 

-1.07 

BAM 

■SB 

0.00 

0.95 

-0.72 

0.00 

0.00 

0.00 

| 

l 

-1.04 

-2.25 

-3.45 

-3.08 

-2.52 

fcllfUl 

-1.50 

-2.31 

-2.06 

-1.69 

2 

1.69 

-1.07 

0.00 

0.00 

BAM 

1.13 

Bi1r>B 

0.00 

0.00 

0.00 


l 

-0.58 

-2.20 

-3.45 

-3.08 

-2.52 

-0.39 

BIEfiB 

-2.31 

-2.06 

-1.69 

2 

1.69 

-1.07 

0.00 

0.00 

0.00 

1.09 

BAM 

BAM 

BEES 

BAMI 


Flat <2:12 (9.46°) 

l 

NA 

NA 

-3.05 

-2.72 

-2.23 

NA 

NA 

-2.27 

-2.03 

-1.66 

2 

NA 

NA 

0.00 

Ilil 

0.00 

NA 

NA 

0.00 

0.00 

0.00 

3:12(14.0°) 

l 

ESS 1 

MFftB 

BAM 

1CTM 


mrxxm 

BKM 

wrxxm 

Biiiti 

EBB 

2 

0.43 

-0.61 

0.00 

0.00 

mmm 

BAMI 

-0.07 

0.00 

0.00 

0.00 

4: 12(18.4°) 

l 

-2.46 

-1.98 

-3.05 

-2.72 

-2.23 

-1.83 

-1.48 

-2.27 

-2.03 

-1.66 

2 

0.85 

-0.S7 


0.00 

0.00 

0.64 

-0.65 

BAM 

BAM 

0.00 

5:12(22.6°) 

l 


EKSKB 

WEEM 

B9 

BIB 

Bllrl 

mmm 

BAM 

BEAM 

warn 

2 

MM 

BflffB 

mmm 

BAM 

BAM 

BAM 

BArJB 


BAM 

iai 

6:12(26.6°) 

1 

■KM 

■JEM 


WMTW 

MEM 

BOOB 

Bg[:l 


BAM 

mwm 

2 



■(HIM 

■♦HIM 

MMM 

B3EB 

BflHB 

MM 

BAtTiB 

BAM 

9:12(36.9°) 

l 

-0.92 

-1.98 

-3.05 

-2.72 

-2.23 

-0.68 

-MS 

-2.27 

-2.03 

-m 

2 

■EIS 

ES2B 

MM 

■lUlTli 

■♦HIM 

BIPB 

WS5M 

BE9 

BAM 

BAM 

12:12(45.0°) 

1 

-0.52 

-0.44 

-3.05 

-2.72 

-2.23 

m\*vm 

EES 

mwm 

mmtu 

EBB 

2 

1,49 

-0.95 

MM 

BAM 

0.00 

19.8 

-12.5 

0.0 

0.0 

0.0 ! 


National Structural Code of the Philippines Volume L 7th Edition, 2015 











































































2-100 CHAPTER 2 - Minimum Design Loads 


Table 207B.6-2 

M WFRS - Part 2; Wind Loads - Roof (kN/m 2 ) 
MWFRS - Roof, V “ 150 -250 kph, h = 27- 36 m 
Exposure C 


3:12 (14.0°) 


4: 12(18.4°) 


5:12(22.6°) 


6:12(26.6°) 


6:12(36.9°) 


12:12(45.0°) 


Flat <2:12 (0.46°) 
3:12(14.0°) 

4: 12(18.4°) 
5:12(22.6°) 
6:12(26.6°) 
9:12(36.9°) 


12:12(45.0°) 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 















CHAPTER 2 - Minimum Design Loads 


Table 207B.6-2 

MWFRS - Part 2: Wind Loads - Roof (kN/m 2 ) 
MWFRS - Roof, V = 300 - 350 kph, ft = 27 - 36 m 
Exposure C 


K (kph) 


Roof Slope 


Rat <2:12 (9.46°) 
3:12(14.0°) 

4: 12(18.4°) 


5:12(22.6°) 


6:12(26.6°) 






nn 




4: 12(18.4°) 


5 : 12 ( 22 . 6 °) 


6:12(26.6°) 


SNV ' 

$C ' 


Flat <2:12 (9.46°) 



3:12(14.0°) 

H§ 


4: 12(18.4°) 

Wl ' 

£{fj, % 

30 

5:12(22.6°) 

$$$& v|y : *f 


6:12(26.6°) 



9:12(36.9°) 

te 


12:12(45.0°) 


Flat <2:12 (9.46°) 


3:12(14.0°) 


4: 12(18.4°) 


5 : 12 ( 22 . 6 °) 


6:12(26.6°) 


9:12(36.9°) 


12:12(45.0°) 


l»l^B!rCT»^tMMi»iMgTiinigiT^MgiT«»iTr«»iTiTMgTi , ail 

I ggMgaCTMfMggUfcMMM IriB B nCTgtjc^ MrMlgEMl 

|g>lrMgf>MMtxilt^||»!lfM| 


IMiBCMMEWIf ■WiltMjMHnyiUMGMMEMMBMl 

lEjBaroiBBiBBiroiillBiBaigil 




National Structural Code of the Philippines Volume I, 7th Edition, 2015 





















CHAPTER 2 - Minimum Design Loads 


Table 207B.6-2 

MWFRS - Part 2: Wind Loads - Roof (kN/m 2 ) 
MWFRS - Roof, V = 150- 250 kph, h = 39 - 48 m 
Exposure C 



5:12(22.6°) 


6:12(26.6°) 



BMlBI— iliMIil MMBP W — M— TOM 



9:12(36.9°) 


12:12(45.0°) 


TJai <2:12 (9.46°) 


3:12(14.0°) 


4: 12(18.4°) 

45 

5:12(22.6°) 


6:12(26.6°) 


9:12(36.9°) 


12:12(45.0°) 



Flat <2:12 (9,46°) 


3:12(14.0°) 


4: 12(18.4°) 
5:12(22.6°) 
6:12(26.6°) 
9:12(36.9°) 











0.00 0.00 






12:! 2 (45.0°) 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 

















CHAPTER 2 - Minimum Design Loads 




Table 207B.6-2 

MWFRS - Part 2: Wind Loads - Roof (kN/m 2 ) 
MWFRS - Roof, V “ 300 - 350 kph, h = 39 - 48 m 
Exposure C 


45 





2 

WMM 


mmrn 

EIiM 

MTtTia 

ilia 

giliM 

WEM 



4 : 12 ( 18 . 4 °) 

1 

Bia 

mbkiM 

mnm 

Bifii 

E XLM 

EMI 


MtWfrM 

ETiM 


2 

MEM 

mwnm 

MM 


Hj'iTiTtlh 

m%zm 

IBM 

EltM 

EW 


5 : 12 ( 22 . 6 °) 

1 

WSEM 

BKltl 

WAM¥m 


Ew 


«EE» 


WSSM 

MWtM 

2 

1.90 

- 1.59 

0.00 

0.00 

0.00 

0.85 

- 0.71 

0.00 

EMI 

Ef 

6 : 12 ( 26 . 6 °) 

l 

- 2.66 

- 3.33 

- 5.12 

- 4.56 

- 3.74 

- 1.18 

- 1.48 

- 2.27 

EMI 

ElftfM 

2 

2,10 

- 1.59 

0.00 

0.00 

0.00 

0.93 

- 0.71 

0.00 

warn 


9 : 12 ( 36 . 9 °) 

1 

- 1.54 

- 3.33 

- 5.12 

- 4.56 

- 3.74 

- 0.68 

- 1.48 

- 2.27 

mvm 

EIMM 

2 

2.51 

- 1.59 

0.00 

0.00 

0.00 

1.12 

- 0,71 

0.00 


ekm 

12 : 12 ( 45 . 0 °) 

1 

- 0.87 

- 3.33 

- 5.12 

- 4.56 

- 3.74 

- 0.39 

- 1.48 

- 2.27 

mwvm 

mwxm 

2 

2.51 

- 1.59 

0.00 

0,00 

0.00 

19.8 

- 12.5 

0.0 

tow 

HEE 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 












CHAPTER 2 - Minimum Design Loads 2-105 


207C.3 Velocity Pressure Table 207C.2-1 

Steps to Determine Wind Loads on MWFRS 

207C.3.1 Velocity Pressure Exposure Coefficient Low-Rise Buildings 


Based on the Exposure Category determined in Section 
207A.7.3, a velocity pressure exposure coefficient K z or 
Kb? as applicable, shall be determined from 
Table 207C.3-1. 

For a site located in a transition zone between exposure 
categories that is near to a change in ground surface 
roughness, intermediate values of K z or K h , between those 
shown in Table 207C.3-1, are permitted, provided that they 
are determined by a rational analysis method defined in the 
recognized literature. 


Step 1: 

Determine occupancy category of building or 
other structure, see Table 103-1 

Step 2: 

Determine the basic wind speed, V, for the 
applicable risk category, see Figure 207A.5- 
1A, B or C 

Step 3: 

Determine wind load parameters: 


> Wind directionality factor, K d , see 
Section 207A.6 and Table 207A.6-1 


> Exposure category B, C or D, see 
Section 207A.7 


> Topographic factor, K zt , see Section 
207A.8 and Figure 207A.8-1 


> Enclosure classification, see 

Section 207A.10 


> Internal pressure coefficient, (GC p i), see 
Section 207A.1 1 and Table 207A.1 1-1 

Step 4: 

Determine velocity pressure exposure 
coefficient, K z or K h , see Tables 207C.3-1 

Step 5: 

Determine velocity pressure, q z or q h , see 
Equation 207C.3-1 

Step 6: 

Determine external pressure coefficient, 
(CG p ), using Figure 207C.4-1 for flat and 
gable roofs. 

User Note: 

See Commentary Figure C207C.4-1 for guidance On hip 
roofs . 

Step 7: Calculate wind pressure, p, from 
Equation 207C.4-1 


National Structural Code of the Philipp 1, 


Volume I, 7th Edition, 2015 


2-106 


CHAPTER 2 Minimum Design Loads 


Commentary: 

See commentary to Section C207B.3.1. 

207C.3.2 Velocity Pressure 

Velocity pressure, q z , evaluated at height z shall be 
calculated by the following equation: 


q z = 0. 613 K z K zt K d V 2 (N/m 2 ); V in m/s (207C.3-1) 


where 


K d = 

wind directionality factor, see Section 
207A.6 

Kz = 

velocity pressure exposure coefficient, see 
Section 207C.3.1 

Kzt = 

topographic factor defined, see Section 
207A.8.2 

V 

basic wind speed, see Section 207A.5.1 

Qz = 

velocity pressure calculated using 

Equation 207C.3-1 at mean roof height h 


The numerical coefficient 0.613 shall be used except where 
sufficient climatic data are available to justify the selection 
of a different value of this factor for a design application. 

Commentary: 

See commentary to Section C207B.3.2 . 

Loads on Main Wind-Force Resisting Systems: 

The pressure coefficients for MWFRS are basically 
separated into two categories: 

1. Directional Procedure for buildings of all heights 
(Figure 207B.4-1) as specified in Section 207B for 
buildings meeting the requirements specified therein. 

2. Envelope Procedure for low-rise buildings 
(Figure 207C.4-1) as specified in Section 207 C for 
buildings meeting the requirements specified therein. 

In generating these coefficients, two distinctly different 
approaches were used. For the pressure coefficients given 
in Figure 207 B. 4-1, the more traditional approach was 
followed and the pressure coefficients reflect the actual 
loading on each surface of the building as a function of 
wind direction, namely, winds perpendicular or parallel to 
the ridge line. 

For low-rise buildings, however, the values of (GC v f) 
represent “pseudo ” loading conditions that, when applied 
to the building, envelop the desired structural actions 


(bending moment, shear, thrust) independent of wind 
direction. To capture all appropriate structural actions 
the building must be designed for all wind directions by 
considering in turn each corner of the building as the 
windward or reference corner shown in the eight sketches 
of Figure 207C.4-1. At each corner, two load patterns are 
applied, one for each wind direction range. The end zone 
creates the required structural actions in the end frame or 
bracing. Note also that for all roof slopes, all eight load 
cases must be considered individually to determine the 
critical loading for a given structural assemblage or 
component thereof. Special attention should be given to 
roof members, such as trusses, which meet the definition of 
MWFRS but are not part of the lateral resisting system . 
When such members span at least from the eave to the ridge 
or support members spanning at least from eave to ridge, 
they are not required to be designed for the higher end zone 
loads under MWFRS. The interior zone loads should be 
applied. This is due to the enveloped nature of the loads for 
roof members. 

To develop the appropriate “pseudo” values of (GC p f), 
investigators at the University of Western Ontario 
(Davenport et al 1978) used an approach that consisted 
essentially of permitting the building model to rotate in the 
wind tunnel through a full 360° while simultaneously 
monitoring the loading conditions on each of the surfaces 
(Figure C207C.4-1). Both Exposures B and C were 
considered. Using influence coefficients for rigid frames, it 
was possible to spatially average and time average the 
surface pressures to ascertain the maximum induced 
external force components to be resisted . More 
specifically, the following structural actions were 
evaluated: 

1. Total uplift. 

2. Total horizontal shear. 

3. Bending moment at knees (two-hinged frame). 

4. Bending moment at knees (three-hinged frame). 

5. Bending moment at ridge (two-hinged frame). 

The next step involved developing sets of “pseudo” 
pressure coefficients to generate loading conditions that 
would envelop the maximum induced force components to 
be resisted for all possible wind directions and exposures. 
Note, for example, that the wind azimuth producing the 
maximum bending moment at the knee would not 
necessarily produce the maximum total uplift. The 
maximum induced external force components determined 
for each of the preceding five categories were used to 
develop the coefficients. The end result was a set of 
coefficients that represent fictitious loading conditions but 
that conservatively envelop the maximum induced force 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-107 


components (bending moment, shear, and thrust) to be 
resisted, independent of wind direction. 

The original set of coefficients was generated for the 
framing of conventional pre-engineered buildings, that is, 
single-storey moment-resisting frames in one of the 
principal directions and bracing in the other principal 
direction. The approach was later extended to single- 
storey moment-resisting frames with interior columns 
(Kavanagh et al. 1983). 

Subsequent wind tunnel studies (isyumov and Case 1995) 
have shown that the (GC p fi) values of Figure 207C.4-1 are 
also applicable to low-rise buildings with structural 
systems other than moment-resisting frames. That work 
examined the instantaneous wind pressures on a low-rise 
building with a 4:12 pitched gable roof and the resulting 
wind-induced forces on its MWFRS. Two different MWFRS 
were evaluated. One consisted = of shear walls and roof 
trusses at different spacing. The other had moment- 
resisting frames in one direction, positioned at the same 
spacing as the roof trusses, and diagonal wind bracing in 
the other direction. Wind tunnel tests were conducted for 
both Exposures B and C. The findings of this study showed 
that the (CC P/ ) values of Figure 207C.4-1 provided 
satisfactory estimates of the wind forces for both types of 
structural systems. This, work confirms the validity of 
Figure 207C.4-1, which reflects the combined action of 
wind pressures on different external surfaces of a building 
and thus takes advantage of spatial averaging. 

In the original wind tunnel experiments, both B and C 
exposure terrains were checked. In these early 
experiments, Exposure B did not include nearby buildings. 
In general, the force components, bending moments, and 
so forth were found comparable in both exposures, 
although ( GC p f ) values associated with Exposure B 
terrain would be higher than that for Exposure C terrain 
because of reduced velocity pressure in Exposure B 
terrain. The ( GC p f ) values given in Figures 207C.4-1, 
207E.4-1, 207E.4-2A, 27E.4-2B, 27E.4-2C, 27E.4-3, 
27E.4-4, 27 E. 4-5 A, 27E.4-5B, and 27 E. 4-6 are derived 
from wind tunnel studies modeled with Exposure C terrain. 
However, they may also be used in other exposures when 
the velocity pressure representing the appropriate 
exposure is used. 

In comprehensive wind tunnel studies conducted by Ho at 
the University of Western Ontario (1992), it was 
determined that when low buildings (h < 18 m) are 
embedded in suburban terrain (Exposure B, which 
included nearby buildings), the pressures in most cases are 
lower than those currently used in existing standards and 
codes, although the values show a very large scatter 
because of high turbulence and many variables. The results 


seem to indicate that some reduction in pressures for 
buildings located in Exposure B is justified. The ASCE 
Task Committee on Wind Loads believes it is desirable to 
design buildings for the exposure conditions consistent 
with the exposure designations defined in the standard \ In 
the case of low buildings, the effect of the increased 
intensity of turbulence in rougher terrain (i.e., Exposure A 
or B us’. C) increases the local pressure coefficients. 
Beginning in NSCP 2001 (ASCE 7-98) the effect of the 
increased turbulence intensity on the loads is treated with 
the truncated profile. Using this approach, the actual 
building exposure is used and the profile truncation 
corrects for the underestimate in the loads that would be 
obtained otherwise. 

Figure 207 C. 4-1 is most appropriate for low buildings with 
width greater than twice their height and a mean roof 
height that does not exceed 10 m. The original database 
included low buildings with width no greater than five 
times their eave height, and eave height did not exceed 
10m. In the absence of more appropriate data, 
Figure 207C.4-1 may also be used for buildings with mean 
roof height that does not exceed the least horizontal 
dimension and is less than or equal to 18m. Beyond these 
extended limits, Figure 207B.4-1 should be used. 

All the research used to develop and refine the low-rise 
building method for MWFRS loads was done on gable- 
roofed buildings. In the absence of research on hip-roofed 
buildings, the ASCE committee has developed a rational 
method of applying Figure 207C.4-1 to hip roofs based on 
its collective experience, intuition, and judgment. This 
suggested method is presented in Figure C207C.4-2. 

Research (Isyumov 1982 and Isyumov and Case 2000) 
indicated that the low-rise method alone underestimates 
the amount of torsion caused by wind loads. In 
ASCE 7-02, Note 5 was added to Figure 207C.4-I to 
account for this torsional effect and has been carried 
forward through subsequent editions. The reduction in 
loading on only 50 percent of the building results in a 
torsional load case without an increase in the predicted 
base shear for the building. The provision will have little 
or no effect on the design of MWFRS that have well- 
distributed resistance. However, it will impact the design 
of systems with centralized resistance, such as a single core 
in the center of the building. An illustration of the intent of 
the note on two of the eight load patterns is shown in 
Figure 207C.4-L All eight patterns should be modified in 
this way as a separate set of load conditions in addition to 
the eight basic patterns. 

Internal pressure coefficients ( GC pi ) to be used for loads 
on MWFRS are given in Table 207 A. 11-1. The internal 
pressure load can be critical in one-storey moment- 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-108 CHAPTER 2 - Minimum Design Loads 


T 


resisting frames and in the top storey of a building where 
the MWFRS consists of moment resisting frames. Loading 
cases with positive and negative internal pressures should 
be considered. The internal pressure load cancels out in 
the determination of total lateral load and base shear. The 
designer can use judgment in the use of internal pressure 
loading for the MWFRS of high-rise buildings . 



Figure C207C.4-1 

Unsteady Wind Loads on Low Buildings for Given Wind Direction {After Ellingwood 1982) 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-109 


207C.4 Wind Loads — Main Wind-Force Resisting 
System 

207C.4.1 Design Wind Pressure for Low-Rise 
Buildings 


207C.4.2 Parapets 

The design wind pressure for the effect of parapets on 
MWFRS of low-rise buildings with flat, gable, or hip roofs 
shall be determined by the following equation: 


Design wind pressures for the MWFRS of low-rise 
buildings shall be determined by the following equation: 


P p = Q P ( GC pn ) (N/m 2 ) (207C.4-2) 


P = Rh[(GC pf ) - ( GC pi )] (N/m 2 ) (207C.4-1) 


where 

<lh 

(GC pf ) 

(GC pi ) 


velocity pressure evaluated at mean roof 
height h as defined in Section 207A.3 
external pressure coefficient from 

Figure 207C.4-1 

internal pressure coefficient from 

Table 207A.11-1 


207C.4.1.1 External Pressure Coefficients ( GC p f ) 


The combined gust effect factor and external pressure 
coefficients for low-rise buildings, (GC p y), are not 
permitted to be separated. 


where 

Pp 


<Ip 


(GC pn ) 


combined net pressure on the parapet due 
to the combination of the net pressures 
from the front and back parapet surfaces. 
Plus (and minus) signs signify net 
pressure acting toward (and away from) 
the front (exterior) side of the parapet 
velocity pressure evaluated at the top of 
the 

parapet 

combined net pressure coefficient 
+ 1.5 for windward parapet 
-1 .0 for leeward parapet 



Commentary: 


Load Case A 



Load Case B 


Figure C207C.4-2 
Hip Roofed Low-Rise Buildings 

Notes: 

1 . Adapt the loadings shown in Figure 207C.4-1 for hip roofed buildings as shown above. For a given hip roof pitch use the roof coefficients from the Case A table for both 
Load Case A and Load Case B. 

2 . The total horizontal shear shall not be less than that determined by neglecting the wind forces on roof surfaces. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 





Windward 


LOAD CASE A 


Direction 


Windward 

Direction 


LOAD CASE B 


Windward 


2-1 1 0 CHAPTER 2 - Minimum Design Loads 


Figure 207C.4-1 

Main Wind Force Resisting System - Part 1 External Pressure Coefficients ( GC pf ) 
Enclosed, Partially Enclosed Buildings, h < 18 m Low-rise Walls and Roofs 


WiadwMd 

Comer 


Wfadwad 


Basic Load Cases 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 






CHAPTFR 2 - Minimum Design Loads 


2-111 


t 


Roof 

LOAD CASE A 

Angle 0 

Building Surface 

(degrees) 

1 

2 

3 

4 

IE 

2E 

3E 

4E 

0-5 

0.40 

-0.69 

-0.37 

-0.29 

0.61 

-1.07 

-0.53 

-0.43 

20 

0.53 

-0.69 

-0.48 

-0.43 

0.80 

-1.07 

-0.69 

-0.64 

30-45 

0.56 

0.21 

-0.43 

-0.37 

0.69 

0.27 

-0.53 

-0.48 

90 

0.56 

0.56 

-0.37 

-0.37 

0.69 

0.69 

-0.48 

-0.48 


Roof 
Angle 6 
(degrees) 

LOAD CASE B 

Building Surface 

1 

2 

3 

4 

5 

6 

IE 

2E 

3E 

4E 

5E 

6E 

0-90 

0.45 

0.69 

0.37 

0.45 

0.4 

0 

0.29 

0.48 

1.07 

0.53 

0.48 

0.61 

0.43 


Notes: 

1 . Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

2. For values of 6 other than those shown, linear interpolation is permitted. 

3. The building must be designed for all wind directions using the 8 loading patterns shown. The load patterns are applied to each building 
comer in turn as the Windward Comer, 

4. Combinations of external and internal pressures (see Table 207 A. 1 1-1) shall be evaluated as required to obtain the most severe loadings. 

5. For the torsional load cases shown below, the pressures in zones designated with a “T” (IT, 2T, 3T, 4T, 5T, 6T) shall be 25% of the full 

design wind pressures (zones 1, 2, 3, 4, 5, 6). 

Exception : One storey buildings with h less than or equal to 9 m> buildings two storeys or less framed with light frame 
construction , and buildings two storeys or less designed with flexible diaphragms need to be designed for the torsional load cases 
Torsional loading shall apply to all eight basic load patterns using the figures below applied at each Windward Comer. 

6. For purposes of designing a building’s MWFRS, the total horizontal shear shall not be less than that determined by neglecting the wind 
forces on the roof. 

Exception: This provision does not apply to buildings using moment frames for the MWFRS. 

7. For flat roofs, use 0 = 0° and locate the zone 2/3 and zone 2E/3E boundary at the mid-width of the building. 

8. The pressure coefficient ( GC p f)> when negative in Zone 2 and 2E, shall be applied in Zone 2/2E for a distance from the edge of the roof 

equal 0.5 times the horizontal dimension of the building parallel to the direction of MWFRS being designed or 2.5 times the eave height 
at the windward wall, whichever is less; the remainder of Zone 2/2E extending to the ridge line shall use the pressure coefficient (GC p ^) 
for zone 3/3E, 

9. Notation: 

a: 1 0% of least horizontal dimension or . 4/i , whichever is smal ler, but not less than either 4% of least horizontal dimension or 0.9 m 
h: Mean roof height, in meters, except that eave height shall be used for 9 < 10°. 

6: Angle of plane of roof from horizontal, in degrees 



Transverse Direction Longitudinal Direction 

Torsional Load Cases 


Figure 207C.4-1 (continued) 

Main Wind Force Resisting System - Part l.External Pressure Coefficients 
Enclosed, Partially Enclosed Buildings, h < 18m Low-rise Walls and Roofs 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-1 12 CHAPTER 2 - Minimum Design Loads 


207C.4.3 Roof Overhangs 

The positive external pressure on the bottom surface of 
windward roof overhangs shall be determined using 
C p = 0. 7 in combination with the top surface pressures 
determined using Figure 207C.4-1. 

207C.4.4 Minimum Design Wind Loads 

The wind load to be used in the design of the MWFRS for 
an enclosed or partially enclosed building shall not be less 
than 0.77 kN/m 2 multiplied by the wall area of the building 
and 0.38 kN/m 2 multiplied by the roof area of the building 
projected onto a vertical plane normal to the assumed wind 
direction. 

Table 207C.3-1 

Velocity Pressure Exposure Coefficients, K h and K z 


Height above 
ground level, z 

Exposure 

i 

m 

B 

C 

D 

0-4.6 

0.70 

0.85 

1.03 

6.1 

0.70 

0.90 

1.08 

7.6 

0.70 

0.94 

1.12 

9.1 

0.70 

0.98 

1.16 

12.2 

0.76 

1.04 

1.22 

15.2 

0.81 

1.09 

1.27 

18 

0.85 

1.13 

1.31 


Notes: 


I . The velocity pressure exposure coefficient K z may be 
determined from the following formula: 

For 4.57 m.< z < z g For z < 4.57 m 


K z = 2. 01 (z/z g ) Z/ “ 


Kz 

= 2.0l(4.57/z g ) 2/ " 


Note: z shall not be taken less than 9 m in exposure B. 

2. a and z g are tabulated in Table 207A.9-1. 

3. Linear interpolation for intermediate values of height 
z is acceptable. 

4. Exposure categories are defined in Section 207A.7. 


Commentary 

This section specifies a minimum wind load to be applied 
horizontally on the entire vertical projection of the building 
as shown in Figure C207B.4-1. This load case is to be 
applied as a separate load case in addition to the normal 
load cases specified in other portions of this chapter. 


Part 2: Enclosed Simple Diaphragm Low-Rj se 
Buildings 

Commentary: 

This simplified approach of the Envelope Procedure is 
for the relatively common low-rise (h < 18m) regular 
shaped, simple diaphragm building case (see definitions 
for “simple diaphragm building ” and " regular-shaped 
building ”) where pressures for the roof and walls can 
be selected directly from a table. Figure 207C.6-1 
provides the design pressures for MWFRS for the 
specified conditions. Values are provided for enclosed 
buildings only ((GC pi ) = ±0.18). 

Horizontal wall pressures are the net sum of the 
windward and leeward pressures on vertical projection 
of the wall. Horizontal roof pressures are the net sum of 
the windward and leeward pressures on vertical 
projection of the roof Vertical roof pressures are the net 
sum of the external and internal pressures on the 
horizontal projection of the roof 

Note that for the MWFRS in a diaphragm building, the 
internal pressure cancels for loads on the walls and for 
the horizontal component of loads on the roof This is 
true because when wind forces are transferred by 
horizontal diaphragms (e.g., floors and roofs) to the 
vertical elements of the MWFRS (e.g., shear walls, X- 
bracing, or moment frames), the collection of wind 
forces from windward and leeward sides of the building 
occurs in the horizontal diaphragms. Once transferred 
into the horizontal diaphragms by the vertically 
spanning wall systems, the wind forces become a net 
horizontal wind force that is delivered to the lateral 
force resisting elements of the MWFRS. There should be 
no structural separations in the diaphragms. 
Additionally, there should be no girts or other horizontal 
members that transmit significant wind loads directly to 
vertical frame members of the MWFRS in the direction 
under consideration. The equal and opposite internal 
pressures on the walls cancel each other in the 
horizontal diaphragm. This simplified approach of the 
Envelope Procedure combines the windward and 
leeward pressures into a net horizontal wind pressure, 
with the internal pressures canceled. The user is 
cautioned to consider the precise application of 
windward and leeward wall loads to members of the 
roof diaphragm where openings may exist and where 
particular members, such as drag struts, are designed. 
The design of the roof members of the MWFRS for 
vertical loads is influenced by internal pressures. The 
maximum uplift, which is controlled by Load Case B, is 
produced by a positive internal pressure. At a roof slope 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 


2-113 


of approximately 20 and above the windward roof 
pressure becomes positive and a negative internal 
pressure used in Load Case 2 in the table may produce 
a controlling case * From 25° to 45°, both positive and 
negative internal pressure cases (Load Cases 1 and 2, 
respectively) must be checked for the roof 

For the designer to use this method for the design of the 
MWFRS, the building must conform to all of the 
requirements listed in Section 207 A. 8. 2; otherwise the 
Directional Procedure, Part 1 of the Envelope 
Procedure, or the Wind Tunnel Procedure must be used. 
This method is based on Part 1 of the Envelope 
Procedure, as shown in Figure 2 07 C. 4-1, for a specific 
group of buildings (simple diaphragm buildings). 
However, the torsional loading from Figure 2 07 C .4-1 is 
deemed to be too complicated for a simplified method. 
The last requirement in Section 207C.6.2 prevents the 
use of this method for buildings with lateral systems that 
are sensitive to torsional wind loading. 

Note 5 of Figure 207 C. 4-1 identifies several building 
types that are known to be insensitive to torsion and may 
therefore be designed using the provisions of 
Section 207C.6. Additionally, buildings whose lateral 
resistance in each principal direction is provided by two 
shear walls, braced frames, or moment frames that are 
spaced apart a distance not less than 75 percent of the 
width of the building measured normal to the orthogonal 
wind direction, and other building types and element 
arrangements described in Section 207B.6.1 or 
207B.6.2 are also insensitive to torsion. This property 
could be demonstrated by designing the building using 
Part 1 of Section 207C, Figure 207C.4-1, and showing 
that the torsion load cases defined in Note 5 do not 
govern the design of any of the lateral resisting 
elements. Alternatively, it can be demonstrated within 
the context of Part 2 of Section 207 C by defining torsion 
load cases based on the loads in Figure 207C.6-1 and 
reducing the pressures on one-half of the building by 75 
percent, as described in Figure 207 C. 4-1, Note 5. If 
none of the lateral elements are governed by these 
torsion cases, then the building can be designed using 
Part 2 of Section 207C; otherwise the building must be 
designed using Part 1 of Section 207B or Part 1 of 
Section 207 C. 

Values are tabulated for Exposure B at h = 9.0 m, and 
K zt = 1.0. Multiplying factors are provided for other 
exposures and heights. The following values have been 
used in preparation of the figures: 


Exposure B 


(GCpi) 

= ±0.18 (enclosed building) 

h 

= 9.0 m 

K d 

= 0.85 


K z = 0. 70 

K zt = TO 

Pressure coefficients are from Figure 207C.4-T 

Wall elements resisting two or more simultaneous wind- 
induced structural actions (e.g., bending, uplift, or 
shear) should be designed for the interaction of the wind 
loads as part of the MWFRS. The horizontal loads in 
Figure 207C.6-1 are the sum of the windward and 
leeward pressures and are therefore not applicable as 
individual wall pressures for the interaction load cases. 
Design wind pressures, p s for zones A and C, should be 
multiplied by + 0.85 for use on windward walls and by - 
0.70 for use on leeward walls (the plus sign signifies 
pressures acting toward the wall surface). For side 
walls, p s for zone C multiplied by - 0.65 should be used. 
These wall elements must also be checked for the 
various separately acting (not simultaneous) component 
and cladding load cases. 

Main wind-force resisting roof members spanning at 
least from the eave to the ridge or supporting members 
spanning at least from eave to ridge are not required to 
be designed for the higher end zone loads. The interior 
zone loads should be applied. This is due to the 
enveloped nature of the loads for roof members. 

207C.5 General Requirements 

The steps required for the determination of MWFRS wind 
loads on enclosed simple diaphragm buildings are shown 
in Table 207C.5-1. 


User Note: 

Part 2 of Section 207 C is a simplified method to 
determine the wind pressure on the MWFRS of enclosed 
simple diaphragm low-rise buildings having a flat, 
gable or hip roof. The wind pressures are obtained 
directly from a table and applied on horizontal and 
vertical projected surfaces of the building. This method 
is a simplification of the Envelope Procedure contained 
in Part 1 of Section 207 C. 


207C.5.1 Wind Load Parameters Specified in Section 
207A 

The following wind load parameters are specified in 
Section 207A: 

• Basic Wind Speed V (Section 207A.5) 

• Exposure category (Section 207A.7) 

Philippines Volume I, 7th Edition, 2015 


National Structural Code of the 


2-114 CHAPTER 2 - Minimum Design Loads 


• Topographic factor K zt (Section 207A.8) 

• Enclosure classification (Section 207A.10) 

Table 207C.5-1 

Steps to Determine Wind Loads on MWFRS Simple 
Diaphragm Low-Rise Buildings 


Step 1 : Determine occupancy category of building or 
other structure, see Table 103-1 

Step 2: Determine the basic wind speed, V, for the 
applicable risk category, see Figure 207A.5- 
1A, B or C 

Step 3: Determine wind load parameters: 

> Exposure category B, C or D, see 
Section 207A.7 

> Topographic factor, K zt , see Section 
207A.8 and Figure 207A.8-1 

Step 4; Enter figure to determine wind pressures for 
h = 9 m, Ps 3 o, see Figure 207C.6-1 

Step 5: Enter figure to determine adjustment for 
building height and exposure, A, see 
Figure 207C.6-1 

Step 6: Determine adjusted wind pressures, p s , see 
Equation 207C.6-1 


207C.6 Wind Loads - Main Wind-Force Ruskm 

System ^ 

207C.6.1 Scope 

A building whose design wind loads are determined i 
accordance with this section shall meet all the condition! 
of Section 207C.6.2. If a building does not meet all of the 
conditions of Section 207C.6.2, then its MWFRS wind 
loads shall be determined by Part 1 of this chapter, by ^ 
Directional Procedure of Section 207B, or by the Wind 
Tunnel Procedure of Section 207F. 

207C.6.2 Conditions 

For the design of MWFRS the building shall comply with 
all of the following conditions: 

1 * The building is a simple diaphragm building as 
defined in Section 207A.2. 

2. The building is a low-rise building as defined in 
Section 207A.2. 

3. The building is enclosed as defined in Section 207A.2 
and conforms to the wind-borne debris provisions of 
Section 207A.10.3. 

4. The building is a regular-shaped building or structure 
as defined in Section 207A.2. 

5. The building is not classified as a flexible building as 
defined in Section 207A.2. 

6. The building does not have response characteristics 
making it subject to across wind loading, vortex 
shedding, instability due to galloping or flutter; and it 
does not have a site location for which channeling 
effects or buffeting in the wake of upwind obstructions 
warrant special consideration. 

7. The building has an approximately symmetrical cross- 
section in each direction with either a flat roof or a 
gable or hip roof with 0 < 45 ° . 

8. The building is exempted from torsional load cases as 
indicated in Note 5 of Figure 207C.4-1, or the torsional 
load cases defined in Note 5 do not control the design 
of any of the MWFRS of the building. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-1 15 
$. 


207C.6.3 Design Wind Loads 

Simplified design wind pressures, p s , for the MWFRS of 
low-rise simple diaphragm buildings represent the net 
pressures (sum of internal and external) to be applied to the 
horizontal and vertical projections of building surfaces as 
shown in Figure 207C.6-1. For the horizontal pressures 
(Zones A, B, C, D), p s is the combination of the windward 
and leeward net pressures. p s shall be determined by the 
following equation: 


207C.6.4 Minimum Design Wind Loads 

The load effects of the design wind pressures from Section 
207C.6.3 shall not be less than a minimum load defined by 
assuming the pressures, p s , for zones A and C equal to 
+766 Pa, Zones B and D equal to +383 Pa, while assuming 
p s for Zones E, F, G, and H are equal to 0.0 Pa. 


Ps — A.KztPs30 (207C.6-1) 

where 

A adjustment factor for building height and 

exposure from Figure 207C.6-1 

K zt topographic factor as defined in 

Section 207A.8 evaluated at mean roof 
height, h 

p S3Q simplified design wind pressure for 

Exposure B, at h = 9 m from Figure 207 C. 6- 
1 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


r 


2-116 CHAPTER 2 - Minimum Design Loads 



Notes: 

1 . Pressures shown are applied to the horizontal and vertical projections, for exposure B, at h = 9 m. Adjust to other exposures and height 
with adjustment factor X. 

2. The load patterns show shall be applied to each comer of the building in turn as the reference comer. (See Figure 207C.4-1) 

3. For Case B use 9 = 0°. 

4. Load cases 1 and 2 must be checked for 25° < 6 < 45°, Load case 2 at 25° is provided only for interpolation between 25° and 30°. 

5. Plus and minus signs signify pressures acting toward and away from the projected surfaces, respectively. 

6. For roof slopes other than those shown, linear interpolation is permitted. 

7. The total horizontal load shall not be less than that determined by assuming p s = 0 in zones B and D. 

8. Where zone E or G falls on a roof overhang on the windward side of the building, use E 0H and G 0H for the pressure on the horizontal 

projection of the overhang. Overhangs on the leeward and side edges shall have the basic zone pressure applied. 

9. Notation: 


a : 10% of least horizontal dimension or 0.4/i, whichever is smaller, but not less than either 4% of least horizontal dimension or 0.9 m 
h : Mean roof height, in meters, except that eave height shall be used for roof angles < 10°. 

0: Angle of plane of roof from horizontal, in degrees. 


Figure 207C.6-1 

Main Wind Force Resisting System - Method 2.Design Wind Pressure 
Enclosed Buildings h < 18 m Walls and Roofs 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-1 1 7 


rr pijsif 

Wind 

Speed 

Roof 

Angle 

(degrees) 

Load 

Case 

Zones 

Horizontal Pressures 

Vertical Pressures 

Overhangs 

A 

B 

C 

D 

E 

F 

G 

H 

EOH 

GOH 

150 

0 to 5° 

1 

0.66 

-0.34 

0.44 

-0.2 

-0.79 

-0.45 

-0.55 

-0.35 

-1.11 

-0.87 

10° 

1 

0.74 

-0.31 

0.49 

-0.18 

-0.79 

-0.48 

-0.55 

-0.37 

-1.11 

-0.87 

15° 

1 

0.83 

-0.27 

0.55 

-0.16 

-0.79 

-0.52 

-0.55 

-0.39 

-1.11 

-0.87 

to 

o 

o 

1 

0.91 

-0.24 

0.61 

-0.13 

-0.79 

-0.55 

-0.55 

-0.42 

-1.11 

-0.87 

25° 

1 

0.83 

0.13 

0.6 

0.14 

-0.37 

-0.5 

-0.27 

-0.41 

-0.68 

-0.58 

2 

0 

0 

0 

0 

1 -0.14 

-0.27 

-0.04 

-0.18 

0 

0 

30 to 45° 

1 

0.74 

0.51 

0.59 

0.41 

0.06 

-0.45 

0.02 

-0.39 

-0,26 

-0.3 

2 

0.74 

0.51 

0.59 

0.41 

0.29 

-0.22 

0.25 

-0.16 

-0.26 

-0.3 

200 

o 

o 

L/l 

o 

1 

1.17 

-0.61 

0.78 

-0.36 

-1.41 

-0.8 

-0.98 

-0.62 

-1.97 

-1.54 

10° 

1 

1.32 

-0.55 

0.88 

-0.32 

-1.41 

-0.86 

-0.98 

-0.67 

-1.97 

-1.54 

15° 

1 

1.48 

-0.48 

0.98 

-0.28 

; -1.41 

-0.92 

-0.98 

-0.7 

-1.97 

-1.54 

20° 

1 

1.62 

-0.43 

1.08 

-0.23 

-1.41 

-0.98 

-0.98 

-0.74 

-1.97 

-1.54 

25° 

1 

1.48 

0.23 

1.07 

0.25 

-0.65 

-0.89 

-0.47 

-0.72 

-1.22 

-1.03 

2 

0 

0 

0 

0 

-0.25 

-0.48 

-0.07 

-0.32 

0 

0 

30 to 45° 

1 

1.32 

0.9 

1.05 

0.72 

0.1 

-0.8 

0.03 

-0.68 

-0.46 

-0.53 

2 

1.32 

0.9 

1.05 

0.72 

0.51 

-0.39 

0.44 

-0.28 

-0.46 

-0.53 

250 

o 

o 

o 

1 

1.83 

-0.95 

1.22 

-0.57 

-2.2 

-1.25 

-1.53 

-0.97 

-3.08 

-2.41 

10° 

1 

2.06 

-0.86 

1.37 

-0.49 

-2.2 

-1.34 

-1.53 

-1.04 

-3.08 

-2.41 

15° 

1 

2.31 

-0.76 

1.53 

-0.44 

-2.2 

-1.44 

-1.53 

-1.09 

-3.08 

-2.41 

20° 

1 

2.53 

-0.67 

1.69 

-0.37 

-2.2 

-1.53 

-1.53 

-1.16 

-3.08 

-2.41 

25° 

1 

2.31 

0.37 

1.67 

0.39 

-1.02 

-1.39 

-0.74 

-1.13 

-1.9 

-1.62 

2 

0 

0 

0 

0 

-0.39 

-0.76 ' 

-0.11 

-0.49 

0 

0 

30 to 45° 

1 

2.06 

1.41 

1.64 

1.13 

0.16 

-1.25 

0.05 

-1.07 

-0.72 

-0.83 

2 

2.06 

1.41 

1.64 

1.13 

0.79 

-0.62 

0.68 

-0.44 

-0.72 

-0.83 


Figure 207C.6-1 

Main Wind Force Resisting System - Method 2 Design Wind Pressure 
Enclosed Buildings h < 18 m Walls and Roofs, Simplified Design Wind Pressure, p S9 0 (Pa) 

(Exposure B at h = 9.0 m with 7=1.0 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-118 CHAPTER 2 - Minimum Design Loads 


Basic 

Wind 

Speed 

(kph) 

Roof 

Angle 

(degrees) 


Zones 


Load 

Case 

Horizontal Pressures 

Vertical Pressures 

Overhanes 

A 

B 

C 

D 

E 

F 

G 

H 

EOH 

COH 


0 to 5° 

1 

2.63 

-1.37 

1.75 

-0.81 

-3.17 

-1.8 

-2.2 

-1.39 

-4.44 

-3.47 ' 

10° 

1 

2.97 

-1.24 

1.98 

-0.71 

-3.17 

-1.93 

-2.2 

-1.49 

-4.44 

-3.47 

300 

15° 

1 

3.32 

-1.09 

2.2 

-0.63 

-3.17 

-2.08 

-2.2 

-1.57 

-4.44 

-3.47 

20° 

1 

3.65 

-0.96 

2.43 

-0.53 

-3.17 

-2.2 

-2.2 

-1.67 

-4.44 

-3.47 

25° 

1 

3.32 

0.53 

2.41 

0.56 

-1.47 

-2 

-1.06 

-1.62 

-2.74 

-2.33 

2 

0 

0 

0 

0 

-0.56 

-1.09 

-0.15 

-0.71 

0 

0 

30 to 45° 

1 

2.97 

2.03 

2.36 

1.62 

0.23 

-1.8 

0.08 

-1.55 

-1.04 

-1.19 

2 

2.97 

2.03 

2.36 

1.62 

1.14 

-0.89 

0.99 

-0.63 

-1.04 

-1.19 

350 

0 to 5° 

1 

3.59 

-1.86 

2.38 

-1.11 

-4.32 

-2.45 

-3 

-1.9 

-6.04 

-4.73 

10° 

1 

4.04 

-1.69 

2.69 

-0.97 

-4.32 

-2.62 

-3 

-2.04 

-6.04 

-4.73 

15° 

1 

4.52 

-1.48 

3 

-0.86 

-4.32 

-2.83 

-3 

-2.14 

-6.04 

-4.73 1 

K) 

O 

o 

1 

4.97 

-1.31 

3.31 

-0.72 

-4.32 

-3 

-3 

-2.28 

-6.04 

-4.73 

25° 

1 

4.52 

0.72 

3.28 

0.76 

-2 

-2.73 

-1.45 

-2.21 

-3.73 

-3.18 

2 

0 

0 

0 

0 

-0.76 

-1.48 

-0.21 

-0.97 

0 

0 

30 to 45° 

1 

4.04 

2.76 

3.21 

, 2.21 

0.31 

-2.45 

0.11 

-2.1 

-1.41 

-1.62 1 

2 

4.04 

2.76 

3.21 

2.21 

1.55 

-1.21 

1.35 

-0.86 

-1.41 

-1.62 


Adjustment Factor for Building Height and Exposure, A 


Mean Roof 
Height (m) 

Exposure 

B 

C 

D 

0-5 

1.0 

1.21 

1.47 

6 

1.0 

1.29 

1.55 

8 

1.0 

1.35 

1.61. 

9 

1.0 

1.40 

1.66 

11 

1.05 

1.45 

1.70 

12 

1.09 

1.49 

1.74 

14 

1.12 

1.53 

1.78 

15 

1.16 

1.56 

1.81 

17 

1.19 

1.59 

1.84 

18 

1.22 

1.62 

1.87 


Figure 207C.6-1 (continued) 

Main Wind Force Resisting System - Method 2 Design Wind Pressure 
Enclosed Buildings h < 18 m Walls and Roofs, Simplified Design Wind Pressure, p S9 . o ( Pa ) 

(Exposure B at h = 9.0 m with / = 1 .0 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


2-119 


CHAPTER 2 - Minimum Design Loads 

i. 


207D Wind Loads on Other Structures and Building 
Appurtenances - MWFRS 

207D.1 Scope 

207D.1.1 Structure Types 

This section applies to the determination of wind loads on 
building appurtenances (such as rooftop structures and 
rooftop equipment) and other structures of all heights (such 
as solid freestanding walls and freestanding solid signs, 
chimneys, tanks, open signs, lattice frameworks, and 
trussed towers) using the Directional Procedure. 

The steps required for the determination of wind loads on 
building appurtenances and other structures are shown in 
Table 207D.1-1. 


User Note: 

Use Section 207D to determine wind pressures on the 
MWFRS of solid freestanding walls, freestanding solid 
signs, chimneys, tanks, open signs, lattice frameworks 
and trussed towers. Wind loads on rooftop structures 
and equipment may be determined from the provisions 
of this chapter. The wind pressures are calculated using 
specific equations based upon the Directional 
Procedure. 


207D.1.2 Conditions 

A structure whose design wind loads are determined in 
accordance with this section shall comply with all of the 
following conditions: 

1. The structure is a regular-shaped structure as defined 
in Section 207A.2. 

2, The structure does not have response characteristics 
making it subject to across-wind loading, vortex 
shedding, or instability due to galloping or flutter; or it 
does not have a site location for which channeling 
effects or buffeting in the wake of upwind obstructions 
warrant special consideration. 

207D.1.3 Limitations 

The provisions of this chapter take into consideration the 
load magnification effect caused by gusts in resonance with 
along-wind vibrations of flexible structures. Structures not 
meeting the requirements of Section 207D.1.2, or having 
unusual shapes or response characteristics, shall be 


designed using recognized literature documenting such 
wind load effects or shall use the Wind Tunnel Procedure 
specified in Section 207F. 

207D.1.4 Shielding 

There shall be no reductions in velocity pressure due to 
apparent shielding afforded by buildings and other 
structures or terrain features. 

207D.2 General Requirements 

207D.2.1 Wind Load Parameters Specified in 
Section 207A 

The following wind load parameters shall be determined in 
accordance with Section 207A: 

• Basic Wind Speed V (Section 207A.5) 

• Wind directionality Factor K d (Section 207A.6) 

• Exposure category (Section 207A.7) 

• Topographic factor K zt (Section 207A.8) 

• Enclosure classification (Section 207 A. 1 0) 

207D.3 Velocity Pressure 

207D.3.1 Velocity Pressure Exposure Coefficient 

Based on the exposure category determined in 
Section 207A.7.3, a velocity pressure exposure coefficient 
K z or K h , as applicable, shall be determined from 
Table 207D.3-1. 

For a site located in a transition zone between exposure 
categories that is near to a change in ground surface 
roughness, intermediate values of K z or K h , between those 
shown in Table 207D.3-1, are permitted, provided that they 
are determined by a rational analysis method defined in the 
recognized literature. 

Commentary : 

See commentary, Section C207B.3.L 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-120 CHAPTER 2 - Minimum Design Loads 


207D.3.2 Velocity Pressure 

Velocity pressure, q z , evaluated at height z shall be 
calculated by the following equation: 


Table 207D.1-1 

Steps to Determine Wind Loads on MWFRS Rooftop 
Equipment and Other Structures 


Step 1 : Determine occupancy category of building or 
other structure, see Table 103-1 

Step 2: Determine the basic wind speed, V , for the 



applicable risk category, see Figure 207A.5- 


where 


1A, B or C 


K d = wind directionality factor, see 

Section 207A.6 

K z = velocity pressure exposure 

coefficient, see Section 207D.3.1 
K zt = topographic factor defined, see 

Section 207A.8.2 


Step 3: Determine wind load parameters: 


> Wind directionality factor, K d , see 
Section 207A.6 and Table 207A.6-1 


> Exposure category B, C or D, see 
Section 207A.7 


V — basic wind speed, see Section 207A.5 

q h = velocity pressure calculated using 

Equation 207D.3-1 at height h 


> Topographic factor, K zt , see 

Section 207A.8 and Figure 207A.8-1 


The numerical coefficient 0.613 shall be used except 
where sufficient climatic data are available to justify the 
selection of a different value of this factor for a design 
application. 


> Gust Effect Factor, G , see Section 207A.9 


Step 4: Determine velocity pressure exposure 


coefficient, K z or see Table 207D.2-1 


Step 5: Determine velocity pressure q z or see 
Equation 207D.3-1 

Step 6: Determine force coefficient, Cf 

> Solid freestanding signs or solid 
freestanding walls, Figure 207D.4-1 

> Chimneys, tanks, rooftop equipment 
Figure 207D.5-1 

> Open signs, lattice frameworks 
Figure 207D.5-2 

> Trussed towers Figure 207D.4-3 
Step 7: Calculate wind force, F : 

> Equation 207D.4-1 for signs and walls 

> Equation 207D.6-1 and Equation 207D.6- 
2 for rooftop structures and equipment 

> Equation 207D.5-1 for other structures 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-121 


Commentary : 

See commentary, Section C207B.3.2. 

Figure 207D.4-1. The force coefficients for solid 
freestanding walls and signs in Figure 207D.4-1 date 
back to ANSI A58. 1-1972. It was shown by Letchford 
(2001) that these data originated from wind tunnel 
studies performed by Flachsbart in the early 1930s in 
smooth uniform flow . The current values in Figure 
207 D. 4-1 are based on the results of boundary layer 
wind tunnel studies (Letchford 1985, 2001, Holmes 
1986, Letchford and Holmes 1994, Ginger et ai 1998a 
and 1998b, and Letchford and Robertson 1999). 

A surface curve fit to Letchford's (2001) and Holmes's 
( 1 986) area averaged mean net pressure coefficient data 
(equivalent to mean force coefficients in this case) is 
given by the following equation 

( 1. 563 + 0. 0042 InO ) - 0. 06148y > j 
C f = j +0. 009011[ln(x)] 2 — 0. 2603y 2 t/o.8 
( — 0. 08393y[ln(jt)] ) 

where x — B/s and y — s/h 

The 0.85 term in the denominator modifies the wind 
tunnel-derived force coefficients into a format where the 
gust effect factor as defined in Section 207A.9 can be 
used. 

Force coefficients for Cases A and B were generated 
from the preceding equation, then rounded off to the 
nearest 0.05. That equation is only valid within the 
range of B/s and s/h ratios given in the figure for Case 
A and B. 

Of all the pertinent studies, only Letchford (2001) 
specifically addressed eccentricity (i.e., Case B). 
Letchford reported that his data provided a reasonable 
match to Cook's (1990) recommendation for using an 
eccentricity of 0.25 times the average width of the sign. 
However, the data were too limited in scope to justify 
changing the existing eccentricity value of 0.2 times the 
average width of the sign, which is also used in the latest 
Australian / New Zealand Standard (Standards 
Australia 2002). 

Case C was added to account for the higher pressures 
observed in both wind tunnel (Letchford 1985, 2001, 
Holmes 1986, Letchford and Holmes 1994, Ginger et al. 
1998a and 1998b, and Letchford and Robertson 1999) 
and full-scale studies (Robertson et al. 1997) near the 
windward edge of a freestanding wall or sign for oblique 
wind directions. Linear regression equations were fit to 


the local mean net pressure coefficient data (for wind 
direction 45°) from the referenced wind tunnel studies 
to generate force coefficients for square regions starting 
at the windward edge. Pressures near this edge increase 
significantly as the length of the structure increases. No 
data were available on the spatial distribution of 
pressures for structures with low aspect ratios (B/s < 
2 ). 

The sample illustration for Case C at the top of 
Figure 207D.4-1 is for a sign with an aspect ratio 
B/s = 4. For signs of differing B/s ratios, the number 
of regions is equal to the number of force coefficient 
entries located below each B/s column heading. 

For oblique wind directions (Case C), increased force 
coefficients have been observed on aboveground signs 
compared to the same aspect ratio walls on ground 
(Letchford 1985, 2001 and Ginger et al 1998a). The 
ratio of force coefficients between above-ground and 
on-ground signs (i.e., s/h = 0. 8 and 1.0, respectively) 
is 1.25, which is the same ratio used in the Australian / 
New Zealand Standard (Standards Australia 2002). 
Note 5 of Figure 207D.4-1 provides for linear 
interpolation between these two cases. 

For walls and signs on the ground (s/h = 1), the mean 
vertical center of pressure ranged from 0. 5Ai to 0. 6 h 
(Holmes 1986, Letchford 1989, Letchford and Holmes 
1994, Robertson et al. 1995, 1996, and Ginger et al. 
1998a) with 0. 55ft being the average value. For 
above-ground walls and signs, the geometric center best 
represents the expected vertical center of pressure. 

The reduction in Cf due to porosity (Note 2) follows a 
recommendation (Letchford 2001). Both wind tunnel 
and full-scale data have shown that return corners 
significantly reduce the net pressures in the region near 
the windward edge of the wall or sign (Letchford and 
Robertson 1999). 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-122 CHAPTER 2 - Minimum Design Loads 


207D.4 Design Wind Loads - Solid Freestanding Walls 
and Solid Signs 

207D.4.1 Solid Freestanding Walls and Solid 
Freestanding Signs 

The design wind force for solid freestanding walls and 
solid freestanding signs shall be determined by the 
following formula: 

F = q h GC f A s (N) (207D.4-1) 

where 

q h = velocity pressure evaluated at height h 
(defined in Figure 207D.4-1) as determined 
in accordance with Section 207D.3.2 

G = gust-effect factor from Section 207 A.9 
Cf = net force coefficient from Figure 207D.4-1 

A s = the gross area of the solid freestanding wall 

or freestanding solid sign, m 2 

207D.4.2 Solid Attached Signs 

The design wind pressure on a solid sign attached to the 
wall of a building, where the plane of the sign is parallel to 
and in contact with the plane of the wall, and the sign does 
not extend beyond the side or top edges of the wall, shall 
be determined using procedures for wind pressures on 
walls in accordance with Section 207E, and setting the 
internal pressure coefficient (GC p 0 equal to 0. 

This procedure shall also be applicable to solid signs 
attached to but not in direct contact with the wall, provided 
the gap between the sign and wall is no more than 0.9 m 
and the edge of the sign is at least 0.9 m in from free edges 
of the wall, i.e., side and top edges and bottom edges of 
elevated walls. 

Commentary: 

Signs attached to walls and subject to the geometric 
limitations of Section 207D.4.2 should experience wind 
pressures approximately equal to the external pressures on 
the wall to which they are attached. The dimension 
requirements for signs supported by frameworks, where 
there is a small gap between the sign and the wall, are 
based on the collective judgment of the committee. 

Figures 207D.5-1, 207D.5-2 and 207D.5-3. With the 
exception of Figure 207D.5-3, the pressure and force 
coefficient values in these tables are unchanged from ANSI 
A58. 1-1972. The coefficients speeijied in these tables are 
based on wind-tunnel tests conducted under conditions of 
uniform flow and low turbulence, and their validity in 


turbulent boundary-layer flows has yet to be completely 
established. Additional pressure coefficients for conditions 
not specified herein may be found in two references (SIA 
1956 and ASCE 1961). 

With regard to Figure 207D.5-3. the force coefficients are 
a refinement of the coefficients specified in ANSI A 58. 1- 
1982 and in ASCE 7-93. The force coefficients specified 
are offered as a simplified procedure that may be used for 
trussed towers and are consistent with force coefficients 
given in ANSI/EIA/TIA-222 E-I99I. Structural Standards 
for Steel Antenna Towers and Antenna Supporting 
Structures, and force coefficients recommended by 
Working Group No. 4 (Recommendations for Guyed 
Masts), International Association for Shell and Spatial 
Structures (1981). 

It is not the intent of this code to exclude the use of other 
recognized literature for the design of special structures, 
such as transmission and telecommunications towers. 
Recommendations for wind loads on tower guys are not 
provided as in previous editions of the code. Recognized 
literature should be referenced for the design of these 
special structures as is noted in Section 207D. 1 .3. lor the 
design of flagpoles, see ANSI/ NAA M M FF 1001-97. 4th 
Ed.. Guide Specifications for Design of Metal Flagpoles. 

207D.5 Design Wind Loads — Other Structures 

The design wind force for other structures (chimneys, 
tanks, rooftop equipment for h > 60 ° , and similar 
structures, open signs, lattice frameworks, and trussed 
towers) shall be determined by the following equation: 

F = q z GC f A f (N) (207D.5-1) 

where 

q z = velocity pressure evaluated at height z as 
defined in Section 207D.3, of the centroid 
of area A f 

G = gust-effect factor from Section 207A.9 
Cf = force coefficients from Figures 207D.5-1 
through 207D.5-3 

A s = projected area normal to the wind except 
where Cf is specified for the actual surface 
area, m 2 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 Minimum Design Loads 2-123 


i 


207D.5.1 Rooftop Structures and Equipment for 

Buildings with h < 18 m 

The lateral force F h on rooftop structures and equipment 
located on buildings with a mean roof height h < 18 in 
shall be determined from Equation 207D.5-2. 

F h = q h {GCy)Af (N) (207D.5-2) 

where 

(GC r ) = 1.9 for rooftop structures and equipment 

with A f less than (0. 1 Bh). ( GCr ) shall be 
permitted to be reduced linearly from 1.9 
to 1.0 as the value of Af is increased from 

(0. 1 Bh) to (Bh) 

q k = velocity pressure evaluated at mean roof 
height of the building 

Af = vertical projected area of the rooftop 
structure or equipment on a plane normal 
to the direction of wind, m 2 

The vertical uplift force, F v , on rooftop structures and 
equipment shall be determined from Equation 207D.5-3. 

F v = q h (GC r )A r (N) (207D.5-3) 

Where 

(GC r ) = 1.5 for rooftop structures and equipment 

with A r less than (0. 1 BL). (GC r ) shall be 
permitted to be reduced linearly from 1.5 
to 1.0 as the value of A r is increased from 

(0. 1 BL) to (BL) 

q h = velocity pressure evaluated at mean roof 
height of the building 

Af = horizontal projected area of rooftop 
structure or equipment, m 2 

Commentary: 

This code requires the use of Figure 207D.5-1 for the 
determination of the wind force on small structures and 
equipment located on a rooftop . Because of the small size 
of the structures in comparison to the building, it is 
expected that the wind force will be higher than predicted 
by Equation 207D.6-1 due to higher correlation of 
pressures across the structure surface, higher turbulence 
on the building roof, and accelerated wind speed on the 
roof 

A limited amount of research is available to provide better 
guidance for the increased force (Hosoya et al 2001 and 
Kopp and Traczuk 2008). Based on this research, the force 
of Equation 207D.6-1 should be increased for units with 


areas that are relatively small with respect to that of the 
buildings they are on. Because GC r is expected to 
approach 1.0 as Af or A r approaches that of the building 
(Bh or BL), a linear interpolation is included as a way to 
avoid a step function in load if the designer wants to treat 
other sizes. The research in Hosoya et al (2001) only 
treated one value of Af (0. 04Bh). The research in Kopp 
and Traczuk (2008) treated values of Af = 0.02 Bh and 
0.03Bh, and values of A r = 0. 0061 BL. 

In both cases the research also showed high uplifts on the 
top of rooftop. Hence uplift load should also be considered 
by the designer and is addressed in Section 207D.6. 

207D.6 Parapets 

Wind loads on parapets are specified in Section 207B.4.5 
for buildings of all heights designed using the Directional 
Procedure and in Section 207C.4.2 for low-rise buildings 
designed using the Envelope Procedure. 

Commentary: 

Prior to the 2002 edition of the standard, no provisions for 
the design of parapets had been included due to the lack of 
direct research. In the 2002 edition of this standard, a 
rational method was added based on the committee's 
collective experience, intuition, and judgment. In the 2005 
edition, the parapet provisions were updated as a result of 
research performed at the University of Western Ontario 
(Mans et al. 2000, 2001) and at Concordia University 
(Stathopoulos et al. 2002a, 2002b). 

Wind pressures on a parapet are a combination of wall and 
roof pressures, depending on the location of the parapet 
and the direction of the wind (Figure C207D.7-1). A 
windward parapet will experience the positive wall 
pressure on its front surface (exterior side of the building) 
and the negative roof edge zone pressure on its back 
surface (roof side). This behavior is based on the concept 
that the zone of suction caused by the wind stream 
separation at the roof eave moves up to the top of the 
parapet when one is present. Thus the same suction that 
acts on the roof edge will also act on the back of the 
parapet. 

The leeward parapet will experience a positive wall 
pressure on its back surface (roof side) and a negative wall 
pressure on its front surface (exterior side of the building). 
There should be no reduction in the positive wall pressure 
to the leeward parapet due to shielding by the windward 
parapet because, typically, they are too far apart to 
experience this effect. Because all parapets would be 
designed for all wind directions, each parapet would in 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-124 CHAPTER 2 - Minimum Design Loads 


turn be the windward and leeward parapet and \ therefore, 
must be designed for both sets of pressures. 

For the design of the MWFRS, the pressures used describe 
the contribution of the parapet to the overall wind loads on 
that system. For simplicity, the front and backpressures on 
the parapet have been combined into one coefficient for 
MWFRS design. The designer should not typically need the 
separate front and back pressures for MWFRS design. The 
internal pressures inside the parapet cancel out in the 
determination of the combined coefficient. The summation 
of these external and internal, front and back pressure 
coefficients is a new term GC pn , the Combined Net 
Pressure Coefficient for a parapet. 

For the design of the components and cladding, a similar 
approach was used. However, it is not possible to simplify 
the coefficients due to the increased complexity of the 
components and cladding pressure coefficients. In 
addition, the front and back pressures are not combined 
because the designer may be designing separate elements 
on each face of the parapet . The internal pressure is 
required to determine the net pressures on the windward 
and leeward surfaces of the parapet. The provisions guide 
the designer to the correct GC p and velocity pressure to 
use for each surface, as illustrated in Figure C207D.7-1. 
Interior walls that protrude through the roof, such as party 
walls and fire walls, should be designed as windward 
parapets for both MWFRS and components and cladding. 


The internal pressure that may be present inside a parapet 
is highly dependent on the porosity of the parapet envelope. 
In other words, it depends on the likelihood of the wall 
surface materials to leak air pressure into the internal 
cavities of the parapet. For solid parapets, such as 
concrete or masonry, the internal pressure is zero because 
there is no internal cavity. Certain wall materials may be 
impervious to air leakage , and as such have little or no 
internal pressure or suction, so using the value of GC pi for 
an enclosed building may be appropriate. However, 
certain materials and systems used to construct parapets 
containing cavities are more porous, thus justifying the use 
of the GC pi values for partially enclosed buildings, or 
higher. Another factor in the internal pressure 
determination is whether the parapet cavity connects to the 
internal space of the building, allowing the building's 
internal pressure to propagate into the parapet. Selection 
of the appropriate internal pressure coefficient is left to the 
judgment of the design professional. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-125 



imnil Hd iBUtiil Piraoet Prewrtt 

(Uwyo tw n U indLTlJdfig Uidy) 

Figure C207D.7-1 
Design Wind Pressures on Parapets 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 




2-126 CHAPTER 2 - Minimum Design Loads 


207D.7 Roof Overhangs 

Wind loads on roof overhangs are specified in 
Section 207B.4.4 for buildings of all heights designed 
using the Directional Procedure and in Section 207C.4.3 
for low-rise buildings designed using the Envelope 
Procedure. 

207D.8 Minimum Design Wind Loading 

The design wind force for other structures shall be not less 
than 0.77 kN/m 2 multiplied by the area Af. 


Table 207D.3-1 Velocity Pressure Exposure Coefficients, Kh and K z 


Height above ground 
level, z (meters) 

Exposure 

B 

c 

D 

0-4.5 

0.572 

0.846 

1.027 

6.0 

0.621 

0.899 

1.080 

7.5 

0.662 

0.942 

1.123 

9.0 

0.697 

0.979 

1.159 

12.0 

0.757 

1.040 

1.218 

15.0 

0.807 

1.090 

1.267 

18.0 

0.850 

1.133 

1.307 

21.0 

0.888 

1.170 

1.343 

24.0 

0.923 

1.204 

1.375 

27.0 

0.955 

1.234 

1.403 

30.0 

0.984 

1.261 

1.429 

36.0 

1.036 

1.311 

1.475 

42.0 

1.083 

1.354 

1.515 

48.0 

1.125 

1.393 

1.551 

54.0 

1.164 

1.428 

1.583 

60.0 

1.199 

1.460 

1.612 

75.0 

1.278 

1.530 

1.676 

90.0 

1.347 

1.590 

1.730 

105.0 

1.407 

1.642 

1.777 

120.0 

1.462 

1.689 

1.819 

135.0 

1.512 

1.731 

1.856 

150.0 

1.558 

1.770 

1.891 


Notes: 

1 . The velocity pressure exposure coefficient K z may be determined from the following formula: 
For 4.5 m< z < z g For z <4.5 m 

K z = 2. 01 (z/z g ) 2/ “ K z = 2 . 01 ( 4 . 57/z g ) V “ 


Commentary >: 

This section specifies a minimum wind load to be ctppftyM 
horizontally on the entire vertical projection of the building 
or other structure, as shown in Figure C207B.4-L This 
load case is to be applied as a separate load case 
addition to the normal load cases specified in other 
portions of this chapter. 


2. The constants a and z g are tabulated in Table 207A.9-1 . 

3. Linear interpolation for intermediate values of height z is permitted. 

4. Exposure categories are defined in Section 207A.7. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 


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Notes: 

1 . The term "signs" in notes below also applies to "freestanding walls". 

2. Signs with openings comprising less than 30% of the gross area are classified as solid signs. Force coefficients for solid signs with 
openings shall be permitted to be multiplied by the reduction factor (1 — (1 — e) 15 ). 

3. To allow for both normal and oblique wind directions, the following cases shall be considered: 

For s/h < 1: 

CASE A: resultant force acts normal to the face of the sign through the geometric center. 

CASE B: resultant force acts normal to the face of the sign at a distance from the geometric center toward the windward 
edge equal to 0.2 times the average width of the sign. 

For B/s > 2, CASE C must also be considered: 

CASE C: resultant forces act normal to the face of the sign through the geometric centers of each region. 

For s/h = 1: 

The same cases as above except that the vertical locations of the resultant forces occur at a distance above the geometric 
center equal to 0.05 times the average height of the sign. 

4. For CASE C where s/h > 0.8, force coefficients shall be multiplied by the reduction factor (1. 8 — s/h). 

5. Linear interpolation is permitted for values of s/h, B/s and L r /s other than shown. 

6. Notation: 

B: horizontal dimension of sign, m; e : ratio of solid area to gross area; 

h: height of the sign, m L r \ horizontal dimension of return comer, m 

s : vertical dimension of the sign, m; 

Figure 207D.4-1 

Design Wind Loads Force Coefficients ( Cf ) Other Structures 
All Heights of Solid Freestanding Walls & Solid Freestanding Signs 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-128 CHAPTER 2 - Minimum Design Loads 



1 . The design wind force shall be calculated based on the area of the structure projected on a plane normal to the wind direction. The 
force shall be assumed to act parallel to the wind direction. 

2. Linear interpolation is permitted for h/D values other than shown. 

3. Notation: 

D: diameter of circular cross-section and least horizontal dimension of square, hexagonal or octagonal cross-sections at elevation 
under consideration, in meters; 

D': depth of protruding elements such as ribs and spoilers, m; and 
h : height of structure, m; and 

q z \ velocity pressure evaluated at height z above ground, N/m 2 

4. For rooftop equipment on buildings with a mean roof height of h < 18 m, use Section 207D.5. 1 . 


Figure 207D.5-1 

Other Structures Force Coefficients, Cf 
Chimneys, Tanks, Rooftop Equipment, & Similar Structures 


ez. 

Flat-Sided 

Rounded Members 


Members 

Djq~ z < 5.3 

Djq~ z > 5.3 

<0.1 

2.0 

1.2 

0.8 

0.1 to 0.29 

1.8 

1.3 

0.9 

0.3 to 0.7 

1.6 

1.5 

1.1 


Notes: 

1. Signs with openings comprising 30% or more of the gross area are classified as open signs. 

2. The calculation of the design wind forces shall be based on the area of all exposed members and elements projected on a plane 
normal to the wind direction. Forces shall be assumed to act parallel to the wind direction. 

3. The area Af consistent with these force coefficients is the solid area projected normal to the wind direction. 

4. Notation: 

e\ ratio of solid area to gross area; 

D: diameter of a typical round member, m; 

q z : velocity pressure evaluated at height z above ground, N/m 2 

Figure 207D.5-2 

Other Structures Force Coefficients, C f All Heights of Open Signs & Lattice Frameworks 


Association of Structural Engineers of the Philippines, Inc, (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-129 


Tower Cross Section 

Cf 

Square 

4. Oe 2 -5.9e +4.0 

Triangle 

3.4e 2 — 4. 7e + 3.4 


Notes: 

1 . For all wind directions considered, the area Af consistent with the specified force coefficients shall be the solid area of a tower face 
projected on the plane of that face for the tower segment under consideration, 

2. The specified force coefficients are for towers with structural angles or similar flat sided members. 

3. For towers containing rounded members, it is acceptable to multiply the specified force coefficients by the following factor when 
determining wind forces on such members: 

0. 51e 2 + 0. 57, but not > 1.0 

4. Wind forces shall be applied in the directions resulting in maximum member forces and reactions. For towers with square cross-sections, 
wind forces shall be multiplied by the following factor when the wind is directed along a tower diagonal: 

1 + 0. 75e, but not > 1.2 

5. Wind forces on tower appurtenances such as ladders, conduits, lights, elevators, etc., shall be calculated using appropriate force 
coefficients for these elements. 

6. Notation: 

e\ ratio of solid area to gross area of one tower face for the segment under consideration. 

Figure 207D.5-2 

Other Structures Force Coefficients, Cf Trussed Towers of All Heights 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-130 CHAPTER 2 - Minimum Design Loads 


207E Wind Loads - Components and Cladding 
(C&C) 

Commentary: 

In developing the set of pressure coefficients applicable for 
the design of components and cladding (C&C) as given in 
Figures 207 E. 4- 1, 207E.4-2A, 207E.4-2B, 207E.4-2C, 
207E.4-3, 207E.4-4, 207E.4-5A, 207E.4-5B, and 207E.4- 
6 , an envelope approach was followed but using different 
methods than for the MWFRS of Figure 2 07 C. 4-1. Because 
of the small effective area that may be involved in the 
design of a particular component (consider, e.g. , the 
effective area associated with the design of a fastener), the 
point wise pressure fluctuations may be highly correlated 
over the effective area of interest. Consider the local purlin 
loads shown in Figure C207C4-L The approach involved 
spatial averaging and time averaging of the point 
pressures over the effective area transmitting loads to the 
purlin while the building model was permitted to rotate in 
the wind tunnel through 360°. As the induced localized 
pressures may also vary widely as a function of the specific 
location on the building, height above ground level, 
exposure, and more importantly, local geometric 
discontinuities and location of the element relative to the 
boundaries in the building surfaces (walls, roof lines), 
these factors were also enveloped in the wind tunnel tests. 
Thus, for the pressure coefficients given in Figures 207E.4- 
1, 207E.4-2A, 207E.4-2B, 207E.4-2C, 207EA-3, 207E.4-4, 
207E.4-5A, 207E.4-5B, and 207E.4-6, the directionality of 
the wind and influence of exposure have been removed and 
the surfaces of the building "zoned” to reflect an envelope 
of the peak pressures possible for a given design 
application. 

As indicated in the discussion for Figure 207C.4-1, the 
wind tunnel experiments checked both Exposure B and C 
terrains. Basically ( GC p ) values associated with Exposure 
B terrain would be higher than those for Exposure C 
terrain because of reduced velocity pressure in Exposure 
B terrain. The ( GC p ) values given in Figures 207E.4-1, 
207E.4-2A, 207E.4-2B, 207E.4-2C , 207E.4-3, 207E.4-4, 
207E.4-5A, 207E.4-5B, and 207E.4-6 are associated with 
Exposure C terrain as obtained in the wind tunnel. 
However, they may also be used for any exposure when the 
correct velocity pressure representing the appropriate 
exposure is used as discussed below. 

The wind tunnel studies conducted by ESDU (1990) 
determined that when low-rise buildings (h < 18 m) are 
embedded in suburban terrain (Exposure B), the pressures 
on components and cladding in most cases are lower than 
those currently used in the standards and codes, although 
the values show a very large scatter because of high 
turbulence and many variables. The results seem to 


indicate that some reduction in pressures for components 
and cladding of buildings located in Exposure B i s 
justified. Hence, the code permits the use of the applicable 
exposure category when using these coefficients. 

The pressure coefficients given in Figure 207 E. 6- 1 for 
buildings with mean height greater than 18 m were 
developed following a similar approach, but the influence 
of exposure was not enveloped (Stathopoulos and 
Dumitrescu-Brulotte 1989). Therefore, exposure 

categories B, C, or D may be used with the values of (GCf) 
in Figure 207E.6-I as appropriate. 

207E.1 Scope 

207E.1.1 Building Types 

This chapter applies to the determination of wind pressures 
on components and cladding (C&C) on buildings. 

1. Part 1 is applicable to an enclosed or partially 
enclosed: 

• Low-rise building (see definition in 

Section 207A.2) 

• Building with h < 18 m 

The building has a flat roof, gable roof, multispan 
gable roof, hip roof, monoslope roof, stepped roof, or 
sawtooth roof and the wind pressures are calculated 
from a wind pressure equation. 

2. Part 2 is a simplified approach and is applicable to an 
enclosed: 

• Low-rise building (see definition in 

Section 207A.2) 

• Building with h < 18 m 

The building has a flat roof, gable roof, or hip roof and 
the wind pressures are determined directly from a 
table. 

3. Part 3 is applicable to an enclosed or partially 
enclosed: 

• Building with h > 18 m 

The building has a flat roof, pitched roof, gable roof, 
hip roof, mansard roof, arched roof, or domed roof and 
the wind pressures are calculated from a wind pressure 
equation. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-131 


4. Part 4 is a simplified approach and is applicable to an 
enclosed: 

• Building with h < 48 m 

The building has a flat roof, gable roof, hip roof, 
monoslope roof, or mansard roof and the wind 
pressures are determined directly from a table. 

5. Part 5 is applicable to an open building of all heights 
having a pitched free roof, monoslope free roof, or 
trough free roof. 

6. Part 6 is applicable to building appurtenances such as 
roof overhangs and parapets and rooftop equipment. 

207E.1.2 Conditions 

A building whose design wind loads are determined in 
accordance with this chapter shall comply with all of the 
following conditions: 

1 . The building is a regular-shaped building as defined in 
Section 207A.2. 

2. The building does not have response characteristics 
making it subject to across wind loading, vortex 
shedding, or instability due to galloping or flutter; or it 
does not have a site location for which channeling 
effects or buffeting in the wake of upwind obstructions 
warrant special consideration. 

207E1.3 Limitations 

The provisions of this chapter take into consideration the 
load magnification effect caused by gusts in resonance with 
along-wind vibrations of flexible buildings. The loads on 
buildings not meeting the requirements of Section 
207E.1.2, or having unusual shapes or response 
characteristics, shall be determined using recognized 
literature documenting such wind load effects or shall use 
the wind tunnel procedure specified in Section 207F. 

207E.1.4 Shielding 

There shall be no reductions in velocity pressure due to 
apparent shielding afforded by buildings and other 
structures or terrain features. 

207E.1.5 Air-Permeable Cladding 

Design wind loads determined from Section 207E shall be 
used for air-permeable cladding unless approved test data 
or recognized literature demonstrates lower loads for the 
type of air-permeable cladding being considered. 


Commentary: 

Air-permeable roof or wall claddings allow partial air 
pressure equalization between their exterior and interior 
surfaces. Examples include siding, pressure-equalized rain 
screen walls, shingles, tiles , concrete roof pavers, and 
aggregate roof surfacing . 

The peak pressure acting across an air-permeable 
cladding material is dependent on the characteristics of 
other components or layers of a building envelope 
assembly . At any given instant the total net pressure across 
a building envelope assembly will be equal to the sum of 
the partial pressures across the individual layers as shown 
in Figure C207E.1-1. However, the proportion of the total 
net pressure borne by each layer will vary from instant to 
instant due to fluctuations in the external and internal 
pressures and will depend on the porosity and stiffness of 
each layer , as well as the volumes of the airspaces between 
the layers . As a result, although there is load sharing 
among the various layers, the sum of the peak pressures 
across the individual layers will typically exceed the peak 
pressure across the entire system. In the absence of 
detailed information on the division of loads, a simple, 
conservative approach is to assign the entire differential 
pressure to each layer designed to carry load. 

To maximize pressure equalization (reduction) across any 
cladding system (irrespective of the permeability of the 
cladding itself), the layer or layers behind the cladding 
should be: 

• relatively stiff in comparison to the cladding material 
and 

• relatively air-impermeable in comparison to the 
cladding material. 

Furthermore, the air space between the cladding and the 
next adjacent building envelope surface behind the 
cladding (e.g., the exterior sheathing) should be as small 
as practicable and compartmentalized to avoid 
communication or venting between different pressure 
zones of a building 's surfaces. 

The design wind pressures derived from Section 207 E 
represent the pressure differential between the exterior and 
interior surfaces of the exterior envelope (wall or roof 
system). Because of partial air-pressure equalization 
provided by air-permeable claddings, the components and 
cladding pressures derived from Section 207E can 
overestimate the load on air-permeable cladding elements . 
The designer may elect either to use the loads derived from 
Section 207 E or to use loads derived by an approved 
alternative method. If the designer desires to determine the 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-132 CHAPTER 2 - Minimum Design Loads 


pressure differential across a specific cladding element in 
combination with other elements comprising a specific 
building envelope assembly, appropriate full-scale 
pressure measurements should be made on the applicable 
building envelope assembly, or reference should be made 
to recognized literature (Cheung and Melbourne 1986 , 
Haig 1990, Baskaran 1992, Southern Building Code 
Congress International 1994, Peterka et ai 1997, ASTM 
2006, 2007, and Kala et ai 2008) for documentation 
pertaining to wind loads. Such alternative methods may 
vary according to a given cladding product or class of 
cladding products or assemblies because each has unique 
features that affect pressure equalization. 



EXTERIOR LAVERySH EATING 
V WALL CAVITY 


CLADDING 


INTERIOR LAYER/FINISH 


BUILDING 

EXTERIOR 


BUILDING 

INTERIOR 


B-R = pressure differential across cladding layer 
fjj-? = pressure dfferential across exterior layer/sheathing 
B-q = pressure dfferential across interior layer/finish 


Figure C207E.1-1 

Distribution of Net Components and Cladding Pressure Acting on a Building Surface 
(Building Envelope) Comprised of Three Components (Layers) 


207E.2 General Requirements 

207E.2.1 Wind Load Parameters Specified in Section 
207A 

The following wind load parameters are specified in 
Section 207A: 


Basic Wind Speed V (Section 207A.5) 

Wind directionality factor K d (Section 207A.6) 
Exposure category (Section 207A.7) 
Topographic factor K zt (Section 207A.8) 

Gust Effect Factor (Section 207A.9) 

Enclosure classification (Section 207 A. 10) 


Association of Structural Engineers of the Philippines, Inc, (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-1 33 


• Internal pressure coefficient ( GC pi ) 

(Section 207A.11). 

207E.2.2 Minimum Design Wind Pressures 

The design wind pressure for components and cladding of 
buildings shall not be less than a net pressure of 0.77 kN/m 2 
acting in either direction normal to the surface. 

207E.2.3 Tributary Areas Greater than 65 m 2 

Component and cladding elements with tributary areas 
greater than 65 m 2 shall be permitted to be designed using 
the provisions for MWFRS. 

207E.2.4 External Pressure Coefficients 

Combined gust effect factor and external pressure 
coefficients for components and cladding, (GC p ), are 
given in the figures associated with this chapter. The 
pressure coefficient values and gust effect factor shall not 
be separated. 

207E.3 Velocity Pressure 

207E.3.1 Velocity Pressure Exposure Coefficient 

Based on the exposure category determined in 
Section 207A.7.3, a velocity pressure exposure coefficient 
K z or K h , as applicable, shall be determined from 
Table 207E.3-1. For a site located in a transition zone 
between exposure categories, that is, near to a change in 
ground surface roughness, intermediate values of K z or 
K h , between those shown in Table 207E.3-1, are permitted, 
provided that they are determined by a rational analysis 
method defined in the recognized literature. 

Commentary: 

See commentary, Section C207B.3.L 

207E.3.2 Velocity Pressure 

Velocity pressure, q z , evaluated at height z shall be 
calculated by the following equation: 


q z = 0. 613 K z K zt K d V 2 (N/m 2 );V in 
m/s 


(207E.3-1) 


where 

Kd 


K zt = topographic factor defined, see 
Section 207A.8 

V = basic wind speed, see Section 207A.5 
q h = velocity pressure calculated using 
Equation 207E.3-1 at height h 

The numerical coefficient 0.613 shall be used except where 
sufficient climatic data are available to justify the selection 
of a different value of this factor for a design application. 

Commentary: 

See commentary, Section C207B.3.2. 

Figures 207E.4-1, 207E.4-2A, 207E.4-2B, and 

207E.4-2C. The pressure coefficient values provided in 
these figures are to be used for buildings with a mean roof 
height of 18 m or less . The values were obtained from wind- 
tunnel tests conducted at the University of Western Ontario 
(Davenport et al 1977, 1978), at the James Cook 
University of North Queensland (Best and Holmes 1978), 
and at Concordia University (Stathopoulos 1981, 
Stathopoulos and Zhu 1988, Stathopoulos and Luchian 
1990, 1992, and Stathopoulos and Saathoff 1991). These 
coefficients were refined to reflect results of full-scale tests 
conducted by the National Bureau of Standards (Marshall 
1977) and the Building Research Station, England (Eaton 
and Moyne 1975). Pressure coefficients for hemispherical 
domes on the ground or on cylindrical structures were 
based on wind-tunnel tests (Taylor 1991). Some of the 
characteristics of the values in the figure are as follows: 

1. The values are combined values of ( GC p ). The gust 
effect factors from these values should not be 
separated. 

2. The velocity pressure q h evaluated at mean roof 
height should be used with all values of (GC V ). 

3. The values provided in the figure represent the upper 
bounds of the most severe values for any wind 
direction. The reduced probability that the design 
wind speed may not occur in the particular direction 
for which the worst pressure coefficient is recorded 
has not been included in the values shown in the 
figure. 

4. The wind-tunnel values, as measured, were based on 
the mean hourly wind speed. The values provided in 
the figures are the measured values divided by (1.53) 2 
(see Figure C207A.5-1) to adjust for the reduced 
pressure coefficient values associated with a 3-s gust 
speed. 


= wind directionality factor, see Section 
207A.6 

= velocity pressure exposure coefficient, see 
Section 207E.3.1 

National Structural Code of the Philippines Volume I, 7th Edition, 2015 


Each component and cladding element should be designed 
for the maximum positive and negative pressures 
(including applicable internal pressures) acting on it. The 


2-134 CHAPTER 2 - Minimum Design Loads 


pressure coefficient values should be determined for each 
component and cladding element on the basis of its 
location on the building and the effective area for the 
element. Research (Stathopoulos and Zhu 1988 , 1990) 
indicated that the pressure coefficients provided generally 
apply to facades with architectural features , such as 
balconies , ribs , and various facade textures . In ASCE 7-02, 
the roof slope range and values of (GC p ) were updated 
based on subsequent studies (Stathopoulos et al. 1999, 
2000 , 2001 ). 

Figures 207E.4-4 , 207E.4-5A, and 207E.4-5B. These 
figures present values of (GC p ) for the design of roof 
components and cladding for buildings with multispan 
gable roofs and buildings with monoslope roofs. The 
coefficients are based on wind tunnel studies (Stathopoulos 
and Mohammadian 1986, Suny and Stathopoulos 1988, 
and Stathopoulos and Saathoff 1991). 

Figure 207E.4-6. The values of ( GC p ) in this figure are for 
the design of roof components and cladding for buildings 
with sawtooth roofs and mean roof height, h, less than or 
equal to 18 m. Note that the coefficients for corner zones 
on segment A differ from those coefficients for corner zones 
on the segments designated as B, C, and D . Also, when the 
roof angle is less than or equal to 10°, values of ( GC p )for 
regular gable roofs (Figure 207E.4-2A) are to be used. The 
coefficients included in Figure 207E.4-6 are based on wind 
tunnel studies reported by Saathoff and Stathopoulos 
(1992). 

Figure 207E.4- 7. This figure for cladding pressures on 
dome roofs is based on Taylor (1991). Negative pressures 
are to be applied to the entire surface, because they apply 
along the full arc that is perpendicular to the wind 
direction and that passes through the top of the dome. 
Users are cautioned that only three shapes were available 
to define values in this figure (h D /D — 0 . 5 , f/D = 
0 . 5 ; h D /D = 0 . 0 , f/D = 0 . 5 ; and h D /D = 0 . 0 , // 
D = 0 . 33 ). 


Figure 207E.6-1. The pressure coefficients shown in this 
figure reflect the results obtained from comprehensive 
wind tunnel studies carried out (Stathopoulos and 
Dumitrescu-Brulotte 1989). The availability of more 
comprehensive wind tunnel data has also allowed a 
simplification of the zoning for pressure coefficients, flat 
roofs are now divided into three zones, and walls are 
represented by two zones. 

The external pressure coefficients and zones given in 
Figure 207E.6-1 were established by wind tunnel tests on 
isolated " box-like " buildings (Akins and Cermak 1975 and 
Peterka and Cermak 1975). Boundary-layer wind-tunnel 
tests on high-rise buildings (mostly in downtown city 
centers) show that variations in pressure coefficients and 
the distribution of pressure on the different building 
facades are obtained (Templin and Cermak 1978). These 
variations are due to building geometry, low attached 
buildings, nonrectangular cross-sections, setbacks, and 
sloping surfaces. In addition, surrounding buildings 
contribute to the variations in pressure. Wind tunnel tests 
indicate that pressure coefficients are not distributed 
symmetrically and can give rise to torsional wind loading 
on the building. 

Boundary-layer wind-tunnel tests that include modeling of 
surrounding buildings permit the establishment of more 
exact magnitudes and distributions of (GCp) for buildings 
that are not isolated or <( boxlike ” in shape. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 


Table 207E.3-1 

Velocity Pressure Exposure Coefficients, K h and K z 


Height above ground level, z 

Exposure 

B 

C 

D 

(m) 

0-4.5 

0.70 

0.85 

1.03 

6.0 

0.70 

0.90 

1.08 

7.5 

0.70 

0.94 

1.12 

9.0 

0.70 

0.98 

1.16 

12.0 

0.76 

1.04 

1.22 

15.0 

0.81 

1.09 

1.27 

18.0 

0.85 

1.13 

1.31 

21.0 

0.89 

1.17 

1.34 

24.0 

0.93 

1.21 

1.38 

27.0 

0.96 

1.24 

1.40 

30.0 

0.99 

1.26 

1.43 

36.0 

1.04 

1.31 

1.48 

42.0 

1.09 

1.36 

1.52 

48.0 

1.13 

1.39 

1.55 

54.0 

1.17 

1.43 

1.58 

60.0 

1.20 

1.46 

1.61 

75.0 

1.28 

1.53 

1.68 

90.0 

1.35 

1.59 

1.73 

105.0 

1.41 

1.64 

1.78 

120.0 

1.47 

1.69 

1.82 

135.0 

1.52 

1.73 

1.86 

150.0 

1.56 

1.77 

1.89 


Notes: 


1 . The velocity pressure exposure coefficient K z may be determined from the following formula: 


For 4.57 m < z < z g For z< 4.57 m 

K z = 2 . 01 (z/z g ) 2/ “ K z = 2. 01(4. 57 /z g ) 2/ “ 

2. a and z g are tabulated in Table 207A.9-1 . 

3. Linear interpolation for intermediate values of height z is acceptable. 

4. Exposure categories are defined in Section 207A.7. 


2-135 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-136 CHAPTER 2 - Minimum Design Loads 




Part 1: Low-Rise Buildings 


207E.4.2 Design Wind Pressures 


Commentary: 

The component and cladding tables in Figure 207E.5-1 are 
a tabulation of the pressures on an enclosed \ regular , 9-m 
high building with a roof as described. The pressures can 
be modified to a different exposure and height with the 
same adjustment factors as the MWFRS pressures . For the 
designer to use this method for the design of the 
components and cladding, the building must conform to all 
five requirements in Section 207 E. 6 ; otherwise one of the 
other procedures specified in Section 207E.1.1 must be 
used. 

207E.4 Building Types 

The provisions of Section 207E.4 are applicable to an 
enclosed and partially enclosed: 

• Low-rise building (see definition in Section 207A.2) 

• Building with h < 1 8 m 

The building has a flat roof, gable roof, multispan gable 
roof, hip roof, monoslope roof, stepped roof, or sawtooth 
roof. The steps required for the determination of wind loads 
on components and cladding for these building types are 
shown in Table 207E.4-1. 

207E.4.1 Conditions 

For the determination of the design wind pressures on the 
components and claddings using the provisions of 
Section 207E.4.2 the conditions indicated on the selected 
figure(s) shall be applicable to the building under 
consideration. 


Design wind pressures on component and cladding 
elements of low-rise buildings and buildings with 
h < 18 m shall be determined from the following equation: 

V = qfc[(CCp) - (GC pi )] (N/m 2 ) 207E.4-1 

where 

q z = velocity pressure evaluated at mean roof 
height h as defined in Section 207E.3 
(GC p ) = external pressure coefficients given in: 

• Figure 207E.4-1 (walls) 

• Figures. 207E.4-2A to 207E.4-2C (flat 
roofs, gable roofs, and hip roofs) 

• Figure 207E.4-3 (stepped roofs) 

• Figure 207E.4-4 (multispan gable roofs) 

• Figures 207E.4-5A and 207E.4-5B 
(monoslope roofs) 

• Figure 207E.4-6 (sawtooth roofs) 

• Figure 207E.4-7 (domed roofs) 

• Figure 207B.4-3, footnote 4 (arched roofs) 

(GC A = internal pressure coefficient given in 
Pl Table 207 A. 11-1 


User Note; 

Use Part 1 of Section 207 E to determine wind pressures 
on C&C of enclosed and partially enclosed low-rise 
buildings having roof shapes as specified in the 
applicable figures. The provisions in Part 1 are based 
on the Envelope Procedure with wind pressures 
calculated using the specified equation as applicable to 
each building surface. For buildings for which these 
provisions are applicable this method generally yields 
the lowest wind pressures of all analytical methods 
contained in this code. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-137 

i 


Table 207E.4-1 

Steps to Determine C&C Wind Loads 
Enclosed and Partially Enclosed 
Low-rise Buildings 


Step 1 : Determine risk category of building or other 
structure, see Table 103-1 

Step 2: Determine the basic wind speed, V, for the 
applicable risk category, see Figure 207A.5- 
1A, BorC 

Step 3: Determine wind load parameters: 

> Wind directionality factor, K d , see 
Section 207A.6 and Table 207A.6-1 

> Exposure category B, C or D, see Section 
207A.7 

> Topographic factor, K zt , see Section 
207 A.8 and Figure 207A.8-1 

> Enclosure classification, see Section 
207 A. 10 


> Internal pressure coefficient, (GC pi ), see 
Section 207A.1 1 and Table 207A.1 1-1 


Step 4: 

Determine 

velocity 

pressure 

exposure 


coefficient 

K z or K h , 

see Table 207E.3-1 

Step 5: 

Determine velocity 
Equation 207E.3-1 

pressure, 

q h , see 

Step 6: 

Determine 

(GC P ) 

external 

pressure 

coefficient, 


> Walls, see Figure 207E.4-1 

> Flat roofs, gable roofs, hip roofs, see 
Figure 207E.4-2 


> Stepped roofs, see Figure 207E.4-3 

> Multispan gable roofs, see Figure 207E.4- 
4 

> Monoslope roofs, see Figure 207E.4-5 

> Sawtooth roofs, see Figure 207E.4-6 

> Domed roofs, see Figure 207E.4-7 

> Arched roofs, see Figure 207B.4-3 
footnote 4 

Step 7 : Calculate wind pressure, p, Equation 207E.4- 1 


Part 2: Low-Rise Buildings (Simplified) 

207E.5 Building Types 

The provisions of Section 207E.5 are applicable to an 
enclosed: 

• Low-rise building (see definition in Section 207A.2) 

• Building with h < 18 m 

The building has a flat roof, gable roof, or hip roof The 
steps required for the determination of wind loads on 
components and cladding for these building types are 
shown in Table 207E.5- 1 . 

207E.5.1 Conditions 

For the design of components and cladding the building 
shall comply with all the following conditions: 

1 . The mean roof height h must be less than or equal to 
18 m (i.e. h < 18 m). 

2. The building is enclosed as defined in 
Section 207A.2 and conforms to the wind-borne debris 
provisions of Section 207A.10.3. 

3. The building is a regular-shaped building or structure 
as defined in Section 207A.2. 

4. The building does not have response characteristics 
making it -subject to across wind loading, vortex 
shedding, or instability due to galloping or flutter; and 
it does not have a site location for which channeling 
effects or buffeting in the wake of upwind obstructions 
warrant special consideration. 

5. The building has either a flat roof, a gable roof with 
9 < 45°, or a hip roof with 0 < 27°. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-138 CHAPTER 2 - Minimum Design Loads 


t 


207E.5.2 Design Wind Pressures 

Net design wind pressures, p nef , for component and 
cladding of buildings designed using the procedure 
specified herein represent the net pressures (sum of internal 
and external) that shall be applied normal to each building 
surface as shown in Figure 207E.5-1. p net shall be 
determined by the following equation: 

Pnet = AK zt Pnet9 (207E.5-1) 

where 

A adjustment factor for building height and 

exposure from Figure 207E.5-1 
K zt = topographic factor as defined in 
Section 207A.8 evaluated at 0.33 mean 
roof height, 0. 33Ji 

Pnet30 = net design wind pressure for Exposure B, 
at h = 9 m, from Figure 207E.5-1 


User Note : 

Part 2 of Section 207E is a simplified method to 
determine wind pressures on C&C of enclosed low-rise 
buildings having flat , gable or hip roof shapes . The 
provisions of Part 2 are based on the Envelope 
Procedure of Part 1 with wind pressures determined 
from a table and adjusted as appropriate. 


Table 207E.5-1 
Steps to Determine C&C 
Wind Loads Enclosed Low-rise Buildings 
(Simplified Method) 


Step Determine risk category, see Table 103-1 
1 : 

Step Determine the basic wind speed, V , for the 

2: applicable risk category, see Figure 207A.5- 

1A, B or C 

Step Determine wind load parameters: 

3: 

> Exposure category B, C or D, see Section 
207A.7 

> Topographic factor, K zt , see Section 
207A.8 and Figure 207A.8-1 

Step Enter figure to determine wind pressures 

4: at h = 9 m., p net9? see Figure 207E.5-1 

Step Enter figure to determine adjustment for 

5: building height and exposure, A, see Figure 

207E.5-1 

Step Determine adjusted wind pressures, p net , see 

6: Equation 207E.5-1. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-139 




Part 3: Buildings with ft > 18 m 


207E.6.2 Design Wind Pressures 


Commentary : 

In Equation 207E.6-1 a velocity pressure term , qi, appears 
that is defined as the “velocity pressure for internal 
pressure determination. ’* The positive internal pressure is 
dictated by the positive exterior pressure on the windward 
face at the point where there is an opening. The positive 
exterior pressure at the opening is governed by the value 
of q at the level of the opening, not q h . For positive internal 
pressure evaluation , q t may conservatively be evaluated at 
height ft (q t = q h ). For low buildings this does not make 
much difference , but for the example of a 91.5-m-tall 
building in Exposure B with the highest opening at 18 m, 
the difference between q 915 and q 1Q represents a 59 
percent increase in internal pressure . This is unrealistic 
and represents an unnecessary degree of conservatism. 
Accordingly , q t = q z for positive internal pressure 
evaluation in partially enclosed buildings where height z 
is defined as the level of the highest opening in the building 
that could affect the positive internal pressure. For 
buildings sited in wind-borne debris regions , glazing that 
is not impact resistant or protected with an impact 
protective system, q t should be treated as an opening. 

207E.6 Building Types 

The provisions of Section 207E.6 are applicable to an 
enclosed or partially enclosed building with a mean roof 
height ft > 18 m with a flat roof, pitched roof, gable roof, 
hip roof, mansard roof, arched roof, or domed roof. The 
steps required for the determination of wind loads on 
components and cladding for these building types are 
shown in Table 207E.6-1. 

207E.6.1 Conditions 

For the determination of the design wind pressures on the 
component and cladding using the provisions of 
Section 207E.6.2, the conditions indicated on the selected 
flgure(s) shall be applicable to the building under 
consideration. 


Design wind pressures on component and cladding for all 
buildings with ft> 18 m shall be determined from the 
following equation: 

p = q{GC p ) - (GC pi ) (N/m 2 ) 207E.6-1 


where 

<7 

q 


qt 


qt 


(GC P ) 


(GCpi) 


q z for windward walls calculated at height z 
above the ground 

q h for leeward walls, side walls, and roofs 
evaluated at height ft 

q h for windward walls, side walls, leeward 
walls, and roofs of enclosed buildings and for 
negative internal pressure evaluation in 
partially enclosed buildings 
q z for positive internal pressure evaluation in 
partially enclosed buildings where height z is 
defined as the level of the highest opening in 
the building that could affect the positive 
internal pressure. For positive internal 
pressure evaluation, q t may conservatively be 
evaluated at height h(qi = qh) 

External pressure coefficients given in: 

• Figure 207E.6-1 for walls and flat roofs 

• Figure 2 07 B. 4- 3, footnote 4, for arched 
roofs 

• Figure 207E.4-7 for domed roofs 

• Note 6 of Figure 207E.6- 1 

Internal pressure coefficient given in 
Table 207A.11-1 


q and q t shall be evaluated using exposure defined in 
Section 207A.1 1-1 

Exception; 

In buildings with a mean roof height ft greater than 18 m 
and less than 27.4 m, (GC P ) values from Figures 207E.4- 
1 through 207E.4-6 shall be permitted to be used if the 
height to width ratio is one or less. 


User Note : 

Section Part 3 of Section 207 E for determining wind 
pressures for C&C of enclosed and partially enclosed 
buildings with h > 18 m having roof shapes as specified 
in the applicable figures. These provisions are based on 
the Directional Procedure with wind pressures 
calculated from the specified equation applicable to 
each building surface. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-140 CHAPTER 2 - Minimum Design Loads 


Table 207E.6-1 

Steps to Determine C&C Wind Loads 
Enclosed and Partially Enclosed 
Building with h > 18 m 


Step 1; 

Determine risk category, see Table 103-1 

Step 2: 

Determine the basic wind speed, V, for the 
applicable risk category, see Figure 207A.5- 
1A, B or C 

Step 3 : 

Determine wind load parameters: 


> 

Wind directionality factor, K& see 
Section 207A.6 and Table 207 A. 6-1 


> 

Exposure category B, C or D, see Section 
207A.7 


> 

Topographic factor, K zt , see Section 
207A.8 and Figure 207A.8-1 


> 

Enclosure classification, see Section 
207A.10 


> 

Internal pressure coefficient, ( GC pi ), see 
Section 207 A. 11 and Table 207A.11-1 

Step 4: 

Determine velocity pressure exposure 
coefficient K z or K see Table 207E.3-1 

Step 5: 

Determine velocity pressure, q h , see Table 
207E.3-1 

Step 6: 

Determine external pressure coefficient, 

(GC P ) 


> 

Walls and flat roofs, (0 < 10°), see 
Figure 207E.6-1 


> 

Gable and hip roofs, see Figure 207E.4-2 
per Note 6 of Figure 207E.6-1 


> 

Arched roofs, see Figure 207B.4-3, 
footnote 4 


> 

Domed roofs, see Figure 207E.4-7 

Step 7; 

Calculate wind pressure, p, Equation 207E.6- 
1 


Part 4: Buildings with h < 48 m (Simplified) 

Commentary : 

This section has been added to ASCE 7-10 to cover the 
common practical case of enclosed buildings up to height 
h=49m. Table 207E. 7-2 includes wall and roof pressures 
for fat roofs (0 < 10°), gable roofs, hip roofs, monoslope 
roofs, and mansard roofs. Pressures are derived from 
Figure 207E.6-1 (flat roofs), Figure 207 E. 4-2 A. B. and C 
(gable and hip roofs), and Figure 207 E. 4-5 A and B 
(monos lope roofs) of Part 3. Pressures were selected for 
each zone that encompasses the largest pressure 
coefficients for the comparable zones from the different 
roof shapes. Thus, for some cases, the pressures tabulated 
are conservative in order to maintain simplicity. The ( GC p ) 
values from these figures were combined with an infernal 
pressure coefficient (+ or 0. 1 8) to obtain a net coefficient 
from which pressures were calculated. The tabulated 
pressures are applicable to the entire zone shown in the 
various figures. 

Pressures are shown for an effective wind area of 0.93 m 2 . 
A reduction factor is also shown to obtain pressures for 
larger effective wind areas. The reduction factors are 
based on the graph of external pressure coefficients shown 
in the figures in Part 3 and are based on the most 
conservative reduction for each zone from the various 
figures. 

207E.7 Building Types 

The provisions of Section 207E.7 are applicable to an 
enclosed building having a mean roof height h < 49 m 
with a flat roof, gable roof, hip roof, monoslope roof, or 
mansard roof. The steps required for the determination of 
wind loads on components and cladding for these building 
types are shown in Table 207E.7-1. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 Minimum Design Loads 


2-141 


207E.7.1 Wind Loads — Components and Cladding 

207E.7.1.1 Wail and Roof Surfaces 

Design wind pressures on the designated zones of wails 
and roofs surfaces shall be determined from 
Table 207E.7-2 based on the applicable basic wind speed 
V , mean roof height h , and roof slope 6. Tabulated 
pressures shall be multiplied by the exposure adjustment 
factor (EAF) shown in the table if exposure is different 
than Exposure C. Pressures in Table 207E.7-2 are based on 
an effective wind area of 0.93 m 2 . Reductions in wind 
pressure for larger effective wind areas may be taken based 
on the reduction multipliers (RF) shown in the table. 
Pressures are to be applied over the entire zone shown in 
the figures. Final design wind pressure shall be determined 
from the following equation: 

V = Ptabie(EAF)(RF)K zt (207E.7-1) 

where 

RF ~ effective area reduction factor from 

Table 207E.7-2 

EAF = Exposure adjustment factor from 
Table 207E.7-2 

K zt = topographic factor as defined in 

Section 207A.8 

207E.7.1.2 Parapets 

Design wind pressures on parapet surfaces shall be based 
on wind pressures for the applicable edge and corner zones 
in which the parapet is located, as shown in 
Table 207E.7-2, modified based on the following two load 
cases: 

• Load Case A shall consist of applying the applicable 
positive wall pressure from the table to the front 
surface of the parapet while applying the applicable 
negative edge or corner zone roof pressure from the 
table to the back surface. 

• Load Case B shall consist of applying the applicable 
positive wall pressure from the table to the back of the 
parapet surface and applying the applicable negative 
wall pressure from the table to the front surface. 


User Note. 

Part 4 of Section 207 E is a simplified method for 
determining wind pressures for C&C of enclosed and 
partially enclosed buildings with h <49 m. having roof 
shapes as specified in the applicable figures. These 
provisions are based on the Directional Procedure from 
Part 3 with wind pressures selected directly from a table 
and adjusted as applicable. 


Table 207E.7-1 

Steps to Determine C&C Wind Loads 
Enclosed Building with h > 48.8 ?n 


Step Determine risk category, see Table 103-1 
1: 

Step Determine the basic wind speed, V , for the 

2: applicable risk category, see Figure 207A.5- 

1A, BorC 

Step Determine wind load parameters: 

3: 

> Exposure category B, C or D, see Section 
207A.7 

Step Enter Table 207E.7-2 to determine pressure on 
4: walls and roof, p, using Equation 207E.7-1. 

Roof types are: 

> Flat roof (0 < 10 °) 

> Gable roof 

> Hip roof 

^ Monoslope roof 

> Mansard roof 

Step Determine topographic factors, K zt , and apply 
5: factor to pressures determined from tables (if 

applicable), see Section 207A.8 


Pressures in Table 207E.7-2 are based on an effective wind 
area of 0.93 m 2 . Reduction in wind pressure for larger 
effective wind area may be taken based on the reduction 
factor shown in the table. Pressures are to be applied to the 
parapet in accordance with Figure 207E.7-1. The height h 
to be used with Figure 207E.7-1 to determine the pressures 
shall be the height to the top of the parapet. Determine final 
pressure from Equation 207E.7-1. 

Commentary : 


Parapet component and cladding wind pressures can be 
obtained from the tables as shown in the parapet figures 

National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-142 CHAPTER 2 - Minimum Design Loads 


from the table. The pressures obtained are slightly 
conservative based on the net pressure coefficients for 
parapets compared to roof zones from Part 3. Two load 
cases must be considered based on pressures applied to 
both windward and leeward parapet surfaces as shown in 
Figure 207E.7-1. 

207E.7.1.3 Roof Overhangs 

Design wind pressures on roof overhangs shall be based on 
wind pressures shown for the applicable zones in Table 
207E.7-2 modified as described herein. For Zones 1 and 2, 
a multiplier of 1.0 shall be used on pressures shown in 
Table 207E.7-2. For Zone 3, a multiplier of 1.15 shall be 
used on pressures shown in Table 207E.7-2. 

Pressures in Table 207E.7-2 are based on an effective wind 
area of 0.93 m 2 . Reductions in wind pressure for larger 
effective wind areas may be taken based on the reduction 
multiplier shown in Table 207E.7-2. Pressures on roof 
overhangs include the pressure from the top and bottom 
surface of overhang. Pressures on the underside of the 
overhangs are equal to the adjacent wall pressures. Refer to 
the overhang drawing shown in Figure 207E.7-2. 
Determine final pressure from Equation 207E.7-1. 


Commentary: 

Component and cladding pressures for roof overhangs can 
be obtained from the tables as shown in Figure 207E. 7-2. 
These pressures are slightly conservative and are based on 
the external pressure coefficients contained in Figure 
207E.4-2A to 207E.4-2C from Part 3. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-143 



Monoslope Roof 


Mansard Roof 


Flat Roof 

0 < 1 0 deg 

l 1 



Gable Roof 



Figure 207E.7-2 


C & C Zones C&C Wall and Roof Pressures, h < 48 m 
Enclosed Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-144 


CHAPTER 2 - Minimum Design Loads 




Roof and Wall Pressures-Components and Cladding 
Exposure Adjustment Factor 



Notes to Component and Cladding Wind Pressure Table: 

1. For each roof form, Exposure C, V and h determine roof and wall cladding pressures for the applicable zone from tables 
above. For other exposures B or D, multiply pressures from table by the appropriate exposure adjustment factor determined 
from figure above. 

2. Interpolation between h values is permitted. For pressures at other V values than shown in the table, multiply table value 
for any given V 'in the table as shown above: 

Pressure at desired V = pressure from table at V ’x[V desired/^ ] 2 

3. Where two load cases are shown, both positive and negative pressures shall be considered. 

4. Pressures are shown for an effective wind area = 0.93 m 2 . For larger effective wind areas, the pressure shown may be 
reduced by the reduction coefficient applicable to each zone. 

Notation: 

h mean roof height (m) 

V Basic wind speed (kph) 

Table 207E.7-2 (continued) 

C & C Zones C&C Wall and Roof Pressures, h < 48 m 
Enclosed Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




CHAPTER 2 - Minimum Design Loads 2-145 


Reduction Factors 
Effective Wind Area 



Reduction Factors 
Effective Wind Area 


Roof Form 

Sign Pressure 

Zone 1 

Zone 2 

Zone 3 

Zone 4 

Zone 5 

Flat 

Minus 

D 

D 

D 

C 

E 

Flat 

Plus 

NA 

NA 

NA 

D 

D 

Gable, Mansard 

Minus 

B 

C 

c 

C 

E 

Gable, Mansard 

Plus 

B 

B 

B 

D 

D 

Hip 

Minus 

B 

C 

c 

C 

E 

Hip 

Plus 

B 

B 

B 

D 

D 

Monoslope 

Minus 

A 

B 

D 

C 

E 

Monoslope 

Plus 

C 

C 

C 

D 

D 

Overhangs 

All 

A 

A 

B 

NA 

NA 


Table 207E.7-2 (continued) 

C & C Effective Wind Area C&C Wall and Roof Pressures, h < 48 m 
Enclosed Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-146 CHAPTER 2 - Minimum Design Loads 


Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 150 -200 kph, ft = 4.5 - 15 m 
Exposure C 


V (kph) 

150 

200 

h (m) 

Roof Form 

Load 

Case 

Zone 

Zone 

1 

2 

3 

4 

5 

1 

2 

3 

4 

5 

15 

Flat Roof 

[ 

2 

-1.5579 

NA 

-2.4453 

NA 

-3.3328 

NA 

-1.0649 

1.0649 

-1.9523 

1.0649 

-2.7696 

NA 

-4.3473 

NA 

-5.9249 

NA 

-1.8932 

1.8932 

-3.4708 

1.8932 

Gable Roof 
Mansard Roof 

1 

2 

-1.1635 

0.6705 

-1.9523 

0.6705 

-2.9384 

0.6705 

-1.2621 

1.1635 

-1.9523 

1 .0649 

-2.0685 

1.1920 

-3.4708 

1.1920 

-5.2238 

1.1920 

-2.2438 

2.0685 

-3.4708 

1.8932 

Hip Roof 

1 

2 

-1.0649 

0.6705 

-1.8537 

0.6705 

-2.7412 

0.6705 

-1.2621 

1.1635 

-1.9523 

1 .0649 

*1.8932 

1.1920 

-3.2955 

1.1920 

-4.8732 

1.1920 

-2.2438 

2.0685 

-3.4708 

1.8932 

Monoslope 

Roof 

1 

2 

-1.3607 

0.5719 

-1.7551 

0.5719 

-3.0370 

0.5719 

-1.2621 

1.1635 

-1.9523 

1 .0649 

-2.4191 

1.0167 

-3.1202 

1.0167 

-5.3990 

1.0167 

-2.2438 

2.0685 

-3.4708 

1.8932 

12 

Flat Roof 

1 

2 

-1.4865 

NA 

-2.3332 

NA 

-3.1799 

NA 

-1.0161 

1.0161 

-1.8628 

1.0161 

-2.6426 

NA 

-4.1479 

NA 

-5.6531 

NA 

-1.8063 

1.8063 

-3.3116 

1.8063 

Gable Roof 
Mansard Roof 

1 

2 

-1.1101 

0.6397 

-1.8628 

0.6397 

-2.8036 

0.6397 

-1.2042 

1.1101 

-1.8628 

1.0161 

-1.9736 

1.1373 

-3.3116 

1.1373 

-4.9841 

1.1373 

-2.1408 

1.9736 

-3.3116 

1.8063 

Hip Roof 

1 

2 

-1.0161 

0.6397 

-1.7687 

0.6397 

-2.6154 

0.6397 

-1.2042 

1.1101 

-1.8628 

1.0161 

■1.8063 

1.1373 

-3.1444 

1.1373 

-4.6496 

1.1373 

-2.1408 

1.9736 

-3.3116 

1.8063 

Monoslope 

Roof 

1 

2 

-1.2983 

0.5457 

-1.6746 

0.5457 

-2.8977 

0.5457 

-1.2042 

1.1101 

-1.8628 

1.0161 

-2.3081 

0.9701 

-2.9771 

0.9701 

-5.1514 

0.9701 

-2.1408 

1.9736 

-3.3116 

1.8063 

9 

Flat Roof 

1 

2 

-1.4007 

NA 

-2.1986 

NA 

-2.9964 

NA 

-0.9574 

0.9574 

-1.7553 

0.9574 

-2.4901 

NA 

-3.9086 

NA 

-5.3270 

NA 

-1.7021 

1.7021 

-3.1206 

1.7021 

Gable Roof 
Mansard Roof 

! 

2 

-1.0461 

0.6028 

-1.7553 

0.6028 

-2.6418 

0.6028 

-1.1347 

1.0461 

-1.7553 

0.9574 

-1.8597 

1.0717 

-3.1206 

1.0717 

-4.6966 

1.0717 

-2.0173 

1.8597 

-3.1206 

1.7021 

Hip Roof 

1 

2 

-0.9574 

0.6028 

-1.6667 

0.6028 

-2.4645 

0.6028 

-1.1347 

1.0461 

-1.7553 

0.9574 

*1.7021 

1.0717 

-2.9629 

1.0717 

-4.3814 

1.0717 

-2.0173 

1.8597 

-3.1206 

1.7021 

Monoslope 

Roof 

1 

2 

-1.2234 

0.5142 

-1.5780 

0.5142 

-2.7305 

0.5142 

-1.1347 

1.0461 

-1.7553 

0.9574 

-2.1749 

0.9141 

-2.8053 

0.9141 

-4.8542 

0.9141 

-2.0173 

1.8597 

-3.1206 

1.7021 

7.5 

Flat Roof 

1 

2 

-1.3435 

NA 

-2.1088 

NA 

-2.8741 

NA 

-0.9184 

0.9184 

-1.6837 

0.9184 

-2.3885 

NA 

-3.7490 

NA 

-5.1096 

NA 

-1.6326 

1.6326 

-2.9932 

1.6326 

Gable Roof 
Mansard Roof 

1 

2 

-1.0034 

0.5782 

-1.6837 

0.5782 

-2.5340 

0.5782 

-1.0884 

1.0034 

-1.6837 

0.9184 

-1.7838 

1.0280 

-2.9932 

1.0280 

-4.5049 

1.0280 

-1.9350 

1.7838 

-2.9932 

1.6326 

Hip Roof 

1 

2 

-0.9184 

0.5782 

-1.5986 

0.5782 

-2.3639 

0.5782 

-1.0884 

1.0034 

-1.6837 

0.9184 

-1.6326 

1 .0280 

-2.8420 

1.0280 

-4.2025 

1.0280 

-1.9350 

1.7838 

-2.9932 

1.6326 

Monoslope 

Roof 

1 

2 

-1.1735 

0.4932 

-1.5136 

0.4932 

-2.6190 

0.4932 

-1.0884 

1.0034 

-1.6837 

0.9184 

-2.0862 

0.8768 

-2.6908 

0.8768 

-4.6561 

0.8768 

-1.9350 

1.7838 

-2.9932 

1.6326 

6 

Flat Roof 

1 

2 

-1.2864 

NA 

-2.0191 

NA 

-2.7518 

NA 

-0.8793 

0.8793 

-1.6120 

0.8793 

-2.2869 

NA 

-3.5895 

NA 

-4.8921 

NA 

-1.5632 

1.5632 

-2.8658 

1.5632 

Gable Roof 
Mansard Roof 

1 

2 







-2.8658 

0.9842 

-4.3132 

0.9842 

-1.8526 

1.7079 

-2.8658 

1.5632 

Hip Roof 

1 

2 

-0.8793 

0.5536 

-1.5306 

0.5536 

-2.2633 

0.5536 

-1.0421 

0.9607 

-1.6120 

0.8793 

-1.5632 

0.9842 

-2.7211 

0.9842 

-4.0237 

0.9842 

-1.8526 

1.7079 

-2.8658 

1.5632 

Monoslope 

Roof 

1 

2 

-1.1235 

0.4722 

-1.4492 

0.4722 

-2.5076 

0.4722 

-1.0421 

0.9607 

-1.6120 

0.8793 

-1.9974 

0.8395 

-2.5763 

0.8395 

-4.4579 

0.8395 

-1.8526 

1.7079 

-2.8658 

1.5632 

4.5 

Flat Roof 

1 

2 

-1.2149 

NA 

-1.9069 

NA 

-2.5990 

NA 

-0.8304 

0.8304 

-1.5225 

0.8304 

-2.1598 

NA 

-3.3901 

NA 

-4.6204 

NA 

-1.4763 

1.4763 

-2.7066 

1.4763 

Gable Roof 
Mansard Roof 

1 

2 

-0.9073 

0.5229 

-1.5225 

0.5229 

-2.2914 

0.5229 

-0.9842 

0.9073 

-1.5225 

0.8304 

-1.6130 

0.9295 

-2.7066 

0.9295 

-4.0736 

0.9295 

-1.7497 

1.6130 

-2.7066 

1.4763 

Hip Roof 

1 

2 

-0.8304 

0.5229 

-1.4456 

0.5229 

-2.1376 

0.5229 

-0.9842 

0.9073 

-1.5225 

0.8304 

-1.4763 

0.9295 

-2.5699 

0.9295 

-3.8002 

0.9295 

-1.7497 

1.6130 

-2.7066 

1.4763 

Monoslope 

Roof 

1 

2 

-1.0611 

0.4460 

-1.3687 

0.4460 

-2.3683 

0.4460 

-0.9842 

0.9073 

-1.5225 

0.8304 

-1.8864 

0.7928 

-2.4332 

0.7928 

-4.2103 

0.7928 

-1.7497 

1.6130 

-2.7066 

1.4763 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



r 


CHAPTER 2 - Minimum Design Loads 


2-147 




Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 250 -300 kph, ft = 4.5 - 15 m 
Exposure C 


V (kph) 

250 

300 

h(m) 

Roof Form 

Load 

Zone 

Zone 

Case 

1 

2 

3 

4 

5 

1 

2 

3 

4 

5 


Flat Roof 

1 

-4.3276 

-6.7926 

-9.2577 

-2.9581 

-5.4232 

-6.2317 

-9.7814 

-13.3311 

-4.2596 

-7.8093 


2 

NA 

NA 

NA 

2.9581 

2.9581 

NA 

NA 

NA 

4.2596 

4.2596 







Gable Roof 

1 

-3.2320 

-5.4232 

-8.1621 

-3.5059 

-5.4232 

-4.6541 

-7.8093 

-11.7534 

-5.0485 

-7.8093 

1 ^ 

Mansard Roof 

2 

1.8625 

1.8625 

1.8625 

3.2320 

2.9581 

2.6820 

2.6820 

2.6820 

4.6541 

4.2596 


Hip Roof 

1 

-2.9581 

-5.1493 

-7.6143 

-3.5059 

-5.4232 

-4.2596 

-7.4149 

-10.9646 

-5.0485 

-7.8093 


2 

1.8625 

1.8625 

1.8625 

3.2320 

2.9581 

2.6820 

2.6820 

2.6820 

4.6541 

4.2596 


Monoslope 

1 

-3.7798 

-4.8754 

-8.4360 

-3.5059 

-5.4232 

-5.4429 

-7.0205 

-12.1479 

-5.0485 

-7.8093 


Roof 

2 

1.5886 

1.5886 

1.5886 

3.2320 

2.9581 

2.2876 

2.2876 

2.2876 

4.6541 

4.2596 


Flat Roof 

1 

-4.1291 

-6.4810 

-8.8330 

-2.8224 

-5.1744 

-5.9458 

-9.3327 

-12.7196 

-4.0642 

-7.4511 


2 

NA 

NA 

NA 

2.8224 

2.8224 

NA 

NA 

NA 

4.0642 

4.0642 


Gable Roof 

1 

-3.0837 

-5.1744 

-7.7877 

-3.3451 

-5.1744 

-4.4406 

-7.4511 

-11.2143 

-4.8169 

-7.4511 

1 7 

Mansard Roof 

2 

1.7771 

1.7771 

1.7771 

3.0837 

2.8224 

2.5590 

2.5590 

2.5590 

4.4406 

4.0642 


Hip Roof 

1 

-2.8224 

-4.9131 

-7.2650 

-3.3451 

-5.1744 

-4.0642 

-7.0748 

-10.4617 

-4.8169 

-7.4511 


2 

1.7771 

1.7771 

1.7771 

3.0837 

2.8224 

2.5590 

2.5590 

2.5590 

4.4406 

4.0642 


Monoslope 

l 

-3.6064 

-4.6517 

-8.0490 

-3.3451 

-5.1744 

-5.1932 

-6.6985 

-11.5906 

-4.8169 

-7.4511 


Roof 

2 

1.5157 

1.5157 

1.5157 

3.0837 

2,8224 

2.1826 

2.1826 

2.1826 

4.4406 

4.0642 


Flat Roof 

1 

-3.8908 

-6.1071 

-8.3234 

-2.6596 

-4.8759 

-5.6028 

-8.7943 

-11.9858 

-3.8298 

-7.0212 


2 

NA 

NA 

NA 

2.6596 

2.6596 

NA 

NA 

NA 

3.8298 

3.8298 


Gable Roof 

1 

-2.9058 

-4.8759 

-7.3384 

-3.1521 

-4.8759 

-4.1844 

-7.0212 

-10.5673 

-4.5390 

-7.0212 

Q 

Mansard Roof 

2 

1.6745 

1.6745 

1.6745 

2.9058 

2.6596 

2.4113 

2.4113 

2.4113 

4.1844 

3.8298 

7 

Hip Roof 

1 

-2.6596 

-4.6296 

-6.8459 

-3.1521 

-4.8759 

-3.8298 

-6.6666 

-9.8581 

-4.5390 

-7.0212 


2 

1.6745 

1.6745 

1.6745 

2.9058 

2.6596 ' 

2.4113 

2.4113 

2.4113 

4.1844 

3.8298 


Monoslope 

1 

-3.3983 

-4.3834 

-7.5847 

-3.1521 

-4.8759 

-4.8936 

-6.3120 

-10.9219 

-4.5390 

-7.0212 


Roof 

2 

1.4283 

1 .4283 

1.4283 

2.9058 

2.6596 

2.0567 

2.0567 

2.0567 

4.1844 

3.8298 


Flat Roof 

1 

-3.7320 

-5.8579 

-7.9837 

-2.5510 

-4.6768 

-5.3741 

-8.4353 

-11.4965 

-3.6735 

-6.7347 


2 

NA 

NA 

NA 

2.5510 

2.5510 

NA 

NA 

NA 

3.6735 

3.6735 


Gable Roof 

1 

-2.7872 

-4.6768 

-7.0389 

-3.0234 

-4.6768 

-4.0136 

-6.7347 

-10,1360 

-4.3537 

-6.7347 

7.5 

Mansard Roof 

2 

1.6062 

1.6062 | 

1.6062 

2.7872 

2.5510 

2.3129 

2*3129 

2.3129 

4.0136 

3.6735 

Hip Roof 

1 

-2.5510 

-4.4406 

-6.5665 

-3.0234 

-4.6768 

-3.6735 

-6.3945 

-9.4557 

-4.3537 

-6.7347 


2 

1.6062 

1 .6062 

1.6062 

2.7872 

2.5510 

2.3129 

2.3129 

2.3129 

4.0136 

3.6735 


Monoslope 

1 

-3.2596 

-4.2044 

-7.2751 

-3.0234 

-4.6768 

-4.6939 

-6.0544 

-10.4761 

-4.3537 

-6.7347 


Roof 

2 

1.3700 

1.3700 

1.3700 

2.7872 

2.5510 

1.9728 

1.9728 

1.9728 

4.0136 

3.6735 


Flat Roof 

1 

-3.5732 

-5.6086 

-7.6440 j 

-2.4425 

-4.4778 

-5.1454 

-8.0764 

-11.0073 

-3.5171 

-6.4481 


2 

NA 

NA 

NA 

2.4425 

2.4425 

NA 

NA 

NA 

3.5171 

3.5171 


Gable Roof 

1 

-2.6686 

-4.4778 

-6.7394 

-2.8948 

-4.4778 

-3.8428 

-6.4481 

-9.7047 

-4.1685 

-6.4481 

£ 

Mansard Roof 

2 

1.5378 

1.5378 

1.5378 

2.6686 

2.4425 

2.2145 

2.2145 

2.2145 

3.8428 

3.5171 

o 

Hip Roof 

1 

-2.4425 

-4.2517 

-6.2871 

-2.8948 

-4.4778 

-3.5171 

-6.1224 

-9.0534 

-4.1685 

-6.4481 


2 

1.5378 

1.5378 

1.5378 

2.6686 

2.4425 

2.2145 

2.2145 

2.2145 

3.8428 

3.5171 


Monoslope 

1 

-3.1209 

-4.0255 

-6.9655 

-2.8948 

-4.4778 

-4.4941 

-5.7968 

-10.0303 

-4.1685 

-6.4481 


Roof 

2 

1.3117 

1.3117 

1.3117 

2.6686 

2.4425 

1.8888 

1.8888 

1.8888 

3.8428 

3.5171 









Flat Roof 

1 

-3.3747 

-5.2970 

-7.2193 

-2.3068 

-4.2291 

-4.8596 

-7.6277 

-10.3958 

-3.3217 

-6.0899 


2 

NA 

NA 

NA 

2.3068 

2.3068 

NA 

NA 

NA 

3.3217 

3.3217 


Gable Roof 

1 

-2.5204 

-4.2291 

-6.3650 

-2.7339 

-4.2291 

-3.6293 

-6.0899 

-9.1655 

-3.9369 

-6.0899 

4.5 

Mansard Roof 

2 

1.4524 

1.4524 

1.4524 

2.5204 

2.3068 

2.0915 

2.0915 

2.0915 

3.6293 

3.3217 

Hip Roof 

1 

-2.3068 

-4.0155 

-5.9378 

-2.7339 

-4.2291 

-3.3217 

-5.7823 

-8.5504 

-3.9369 

-6.0899 


2 

1.4524 

1.4524 

1.4524 

2.5204 

2.3068 

2.0915 

2.0915 

2.0915 

3.6293 

3.3217 


Monoslope 

1 

-2.9475 

-3.8019 

-6.5785 

-2.7339 

-4.2291 

-4.2444 

-5.4747 

-9.4731 

-3.9369 

-6.0899 


Roof 

2 

1.2388 

1.2388 

1.2388 

2.5204 

2.3068 

1.7839 

1.7839 

1.7839 

3.6293 

3.3217 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-148 CHAPTER 2 - Minimum Design Loads 

4 


Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 350 kph, h = 4.5 - 15 m 
Exposure C 


V (kph) 

350 

/i(m) 

Roof Form 

Load 

Zone 

Case 

1 

2 

3 

4 

5 



1 

-8.4820 

-13.3136 

-18.1451 

-5.7978 

-10.6294 


Flat Roof 

2 

NA 

NA 

NA 

5.7978 

5.7978 


Gable Roof 

1 

-6.3347 

-10.6294 

-15.9978 

-6.8715 

-10.6294 


Mansard Roof 

2 

3.6505 

3.6505 

3.6505 

6.3347 

5.7978 

15 


1 

-5.7978 

-10.0925 

-14,9241 

-6.8715 

-10.6294 


Hip Roof 

2 

3.6505 

3.6505 

3.6505 

6.3347 

5.7978 


Monoslope 

l 

-7.4084 

-9.5557 

-16.5346 

-6.8715 

-10.6294 


Roof 

2 

3.1137 

3.1137 

3.1137 

6.3347 

5.7978 



1 

-8.0929 

-12.7029 

-17.3128 

-5.5319 

-10.1418 


Flat Roof 

2 

NA 

NA 

NA 

5.5319 

5.5319 1 


Gable Roof 

1 

-6.0441 

-10.1418 

-15.2639 

-6.5563 

-10.1418 


Mansard Roof 

2 

3.4830 

3.4830 

3.4830 

6.0441 

5.5319 

12 


1 

-5.5319 

-9.6296 

-14.2395 

-6.5563 

-10.1418 


Hip Roof 

2 

3.4830 

3.4830 

3.4830 

6.0441 

5.5319 


Monoslope 

1 

-7.0685 

-9.1174 

-15.7761 

-6.5563 

-10.1418 


Roof 

2 

2.9708 

2.9708 

2.9708 

6.0441 

5.5319 



I 

-7.6260 

-11.9700 

-16.3139 

-5.2127 

-9.5567 


Flat Roof 

2 

NA 

NA 

NA 

5.2127 

5.2127 


Gable Roof 

1 

-5.6954 

-9.5567 

-14.3833 

-6.1781 

-9.5567 


Mansard Roof 

2 

3.2821 

3.2821 

3.2821 

5.6954 

5.2127 

9 


1 

-5.2127 

-9.0740 

-13.4180 

-6.1781 

-9.5567 


Hip Roof 

2 

3.2821 

3.2821 

3.2821 

5.6954 

5.2127 


Monoslope 

1 

-6.6607 

-8.5914 

-14.8660 

-6.1781 

-9.5567 


Roof 

2 

2.7994 

2.7994 

2.7994 

5.6954 

5.2127 



1 

-7.3148 

-11,4814 

-15.6481 

-5.0000 

-9.1666 


Flat Roof 

2 

NA 

NA 

NA 

5.0000 

5.0000 


Gable Roof 

1 

-5.4629 

-9.1666 

-13.7962 

-5.9259 

-9.1666 


Mansard Roof 

2 

3.1481 

3.1481 

3.1481 

5.4629 

5.0000 

7.5 


1 

-5.0000 

-8.7037 

-12.8703 

-5.9259 

-9.1666 


Hip Roof 

2 

3.1481 

3.1481 

3.1481 

5.4629 

5.0000 


Monoslope 

1 

-6.3889 

-8.2407 

-14.2592 

-5.9259 

-9.1666 


Roof 

2 

2.6852 

2.6852 

2.6852 

5.4629 

5.0000 



1 

-7.0035 

-10.9929 

-14.9822 

-4.7872 

-8.7766 


Flat Roof 

2 

NA 

NA 

NA 

4.7872 

4.7872 


Gable Roof 

l 

-5.2305 

-8.7766 

-13.2092 

-5.6737 

-8.7766 


Mansard Roof 

2 

3.0142 

3.0142 

3.0142 

5.2305 

4.7872 

6 


1 

-4.7872 

-8.3333 

-12.3226 

-5.6737 

! -8.7766 


Hip Roof 

2 

3.0142 

3.0142 

3.0142 

5.2305 

4.7872 


Monoslope 

1 

-6.1170 

-7.8900 

-13.6524 

-5.6737 

-8.7766 


Roof 

2 

2.5709 

2.5709 

2.5709 

5.2305 

4.7872 



1 

-6.6144 

-10.3821 

-14.1498 

-4.5213 

-8.2890 


Flat Roof 

2 

NA 

NA 

NA 

4.5213 

4.5213 


Gable Roof 

1 

-4.9399 

-8.2890 

-12.4753 

-5.3585 

-8.2890 


Mansard Roof 

2 

2.8467 

2.8467 

2.8467 

4.9399 

4.5213 

4.5 


1 

-4.5213 

-7.8703 

-11.6380 

-5.3585 

-8.2890 


Hip Roof 

2 

2.8467 

2.8467 

2.8467 

4.9399 

4.5213 


Monoslope 

1 

-5.7772 

-7.4517 

-12.8939 

-5.3585 

-8.2890 


Roof 

2 

2.4281 

2.4281 

| 2.4281 

' 4.9399 

4.5213 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 


2-149 


Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 1 50 -200 kph, h = 1 8 - 33 m 
Exposure C 


V (kph) 

150 

200 

h(m) 

Roof Form 

Load 

Case 

Zone 

Zone 

1 

2 

3 

4 

5 

1 

2 

3 

4 

5 

33 

Flat Roof 

1 

2 

-1.8438 

NA 

-2.8940 

NA 

-3.9443 

NA 

-1.2603 

1.2603 

-2.3106 

1.2603 

-3.2778 

NA 

-5.1450 

NA 

-7.0121 

NA 

-2.2405 

2.2405 

-4.1077 

2.2405 

Gable Roof 
Mansard Roof 

1 

2 

-1.3770 

0.7935 

-2.3106 

0.7935 

-3.4775 

0.7935 

-1.4937 

1.3770 

-2.3106 

1.2603 

-2.4480 

1.4107 

-4.1077 

1.4107 

-6.1822 

1.4107 

-2.6555 

2.4480 

-4.1077 

2.2405 

Hip Roof 

1 

2 

-1.2603 

0.7935 

-2.1939 

0.7935 

-3.2441 

0.7935 

-1.4937 

1.3770 

-2.3106 

1.2603 

-2.2405 

1.4107 

-3.9002 

1.4107 

-5.7673 

1.4107 

-2.6555 

2.4480 

-4.1077 

2.2405 

Monoslope 

Roof 

1 

2 

-1.6104 

0.6768 

-2.0772 

0.6768 

-3.5942 

0.6768 

-1.4937 

1.3770 

-2.3106 

1.2603 

-2.8629 

1 .2033 

-3.6927 

1.2033 

-6.3897 

1.2033 

-2.6555 

2.4480 

-4.1077 

2.2405 

30 

Flat Roof 

1 

2 

-1.8009 

NA 

-2.8267 

NA 

-3.8526 

NA 

-1.2310 

1.2310 

-2.2568 

1.2310 

-3.2016 

NA 

-5.0253 

NA 

-6.8490 

NA 

-2.1884 

2.1884 

-4.0121 

2.1884 

Gable Roof 
Mansard Roof 

1 

2 

-1.3450 

0.7751 

-2.2568 

0.7751 

-3.3966 

0.7751 

-1.4590 

1.3450 

-2.2568 

1.2310 

-2.3911 

1.3779 

-4.0121 

1.3779 

-6.0385 

1.3779 

-2.5937 

2.3911 

-4.0121 

2.1884 

Hip Roof 

1 

2 

-1.2310 

0.7751 

-2.1428 

0.7751 

-3.1687 

0.7751 

-1.4590 

1.3450 

-2.2568 

1.2310 

-2.1884 

1.3779 

-3.8095 

1.3779 

-5.6332 

1.3779 

-2.5937 

2.3911 

-4.0121 

2.1884 

Monoslope 

Roof 

t 

2 

-1.5729 

0.6611 

-2.0289 

0.6611 

-3.5106 

0,6611 

-1.4590 

1.3450 

-2.2568 

1.2310 

-2.7963 

1.1753 

-3.6069 

1.1753 

-6.2411 

1.1753 

-2.5937 

2.3911 

-4.0121 

2.1884 

27 

Flat Roof 

t 

2 

-1.7723 

NA 

-2.7819 

NA 

-3.7914 

NA 

-1.2115 

1.2115 

-2.2210 

1.2115 

-3.1508 

NA 

-4.9455 

NA 

-6.7403 

NA 

-2.1537 

2.1537 

-3.9485 

2.1537 

Gable Roof 
Mansard Roof 

1 

2 

-1.3236 

0.7628 

-2.2210 

0.7628 

-3.3427 

0.7628 

-1.4358 

1.3236 

-2.2210 

1.2115 

-2.3531 

1.3560 

-3.9485 

1.3560 

-5.9426 

1.3560 

-2.5525 

2.3531 

-3.9485 
2.1537 | 

Hip Roof 

-1 

2 

-1.2115 

0.7628 

-2.1088 

0.7628 

-3.1184 

0.7628 

-1.4358 

1.3236 

-2.2210 

1.2115 

-2.1537 

1.3560 

-3.7490 

1.3560 

-5.5438 

1.3560 

-2.5525 

2.3531 

-3.9485 

2.1537 

Monoslope 

Roof 

1 

2 

-1.5480 

0.6506 

-1.9967 

0.6506 

-3.4549 

0.6506 

-1.4358 

1.3236 

-2.2210 

1.2115 

-2.7520 

1.1566 

-3,5496 

1.1566 

-6.1420 

1.1566 

-2.5525 

2.3531 

-3.9485 

2.1537 

24 

Flat Roof 

1 

2 

-1.7294 

NA 

-2.7146 

NA 

-3.6997 

NA 

-1.1821 

1.1821 

-2.1673 

1.1821 

-3.0746 

NA 

-4.8259 

NA 

-6.5772 

NA 

-2.1016 

2.1016 

-3.8529 

2.1016 

Gable Roof 
Mansard Roof 

1 

2 

-1.2916 

0.7443 

-2.1673 

0.7443 

-3.2619 

0.7443 

-1.4011 

1.2916 

-2.1673 

1.1821 

-2.2962 

1.3232 

-3.8529 

f.3232 

-5.7988 

1.3232 

-2.4908 

2.2962 

-3.8529 

2.1016 

Hip Roof 

1 

2 

-1.1821 

0.7443 

-2.0578 

0.7443 

-3.0429 

0.7443 

-1.4011 

1.2916 

-2.1673 

1.1821 

-2.1016 

1.3232 

-3.6583 

1.3232 

-5.4097 

1.3232 

-2.4908 

2.2962 

-3.8529 

2.1016 

Monoslope 

Roof 

1 

2 

-1.5105 

0.6349 

-1.9484 

0.6349 

-3.3713 

0.6349 

-1.4011 

1.2916 

-2.1673 

1.1821 

-2.6854 

1.1286 

-3.4637 

1.1286 

-5.9934 

1.1286 

-2.4908 

2.2962 

-3.8529 

2.1016 

21 

Flat Roof 

1 

2 

-1.6723 

NA 

-2.6248 

NA 

-3.5774 

NA 

-1.1431 

1.1431 

-2.0956 

1.1431 

-2.9729 

NA 

-4.6664 

NA 

-6.3598 

NA 

-2.0321 

2.0321 

-3.7256 

2.0321 

Gable Roof 
Mansard Roof 

1 

2 

-1.2489 

0.7197 

-2.0956 

0.7197 

-3.1540 

0.7197 

-1.3547 

1.2489 

-2.0956 

1.1431 

-2.2203 

1.2795 

-3.7256 

1.2795 

-5.6072 

1.2795 

■2.4084 

2.2203 

-3.7256 

2.0321 

Hip Roof 

1 

2 

-1.1431 

0.7197 

-1.9898 

0.7197 

-2.9423 

0.7197 

-1.3547 

1.2489 

-2.0956 

1.1431 

-2.0321 

1.2795 

-3.5374 

1.2795 

-5.2308 

1.2795 

-2.4084 

2.2203 

-3.7256 

2.0321 

Monoslope 

Roof 

1 

2 

-1.4606 

0.6139 

-1.8839 

0,6139 

-3.2599 

0.6139 

-1.3547 

1.2489 

-2.0956 

1.1431 

-2.5966 

1.0913 

-3.3492 

1.0913 

-5.7953 

1.0913 

-2.4084 

2.2203 

-3.7256 

2.0321 









18 

Flat Roof 

1 

2 

-1.6151 

NA 

-2.5351 

NA 

-3.4551 

NA 

-1,1040 

1.1040 

-2.0240 

1.1040 

-2.8713 

NA 

-4.5068 

NA 

-6.1424 

NA 

-1.9626 

1.9626 

-3.5982 

1.9626 

Gable Roof 
Mansard Roof 

1 

2 

-1.2062 

0.6951 

-2.0240 

0.6951 

-3.0462 

0.6951 

-1.3084 

1.2062 

-2.0240 

1.1040 

-2.1444 

1.2357 

-3.5982 

1.2357 

-5.4155 

1.2357 

-2.3261 

2.1444 

-3.5982 

1.9626 

Hip Roof 

1 

2 

-1.1040 

0.6951 

-1.9218 

0.6951 

-2.8417 

0.6951 

-1.3084 

1.2062 

-2.0240 

1.1040 

-1.9626 

1.2357 

-3.4165 

1.2357 

-5.0520 

1.2357 

-2.3261 

2.1444 

-3.5982 

1.9626 

Monoslope 

Roof 

1 

2 

-1.4107 

0.5929 

-1.8195 
0.5929 , 

-3.1484 

0.5929 

-1.3084 

1.2062 

-2.0240 

1.1040 

-2.5078 

1.0540 

-3.2347 

1.0540 

-5.5972 

1 .0540 

-2.3261 

2.1444 

-3.5982 

1.9626 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-150 CHAPTER 2 - Minimum Design Loads 


» 


Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 250 -300 kph, h = 18 - 33 m 
Exposure C 


V (kph) 

250 

300 



Load 

Zone 

Zone 


h (m) 

Roof Form 

Case 

1 

2 

3 

4 

5 

1 

2 

3 

4 

5 



I 

-5.1216 

-8.0390 

-10.9564 

-3.5009 

-6.4182 

-7.3751 

-11.5761 

-15.7772 

-5.0412 

-9.2422 


Flat Roof 

2 

NA 

NA 

NA 

3.5009 

3.5009 

NA 

NA 

NA 

5.0412 

5.0412 


Gable Roof 

1 

-3.8250 

-6.4182 

-9.6598 

-4.1492 

-6.4182 

-5.5080 

-9.2422 

-13.9100 

-5.9748 

-9.2422 


Mansard Roof 

2 

2.2042 

2.2042 

2.2042 

3.8250 

3.5009 

3.1741 

3.1741 

3.1741 

5.5080 

5.0412 

33 


l 

-3.5009 

-6.0941 

-9.0114 

-4.1492 1 

-6.4182 

-5.0412 

-8.7755 

-12.9765 

-5.9748 

-9.2422 


Hip Roof 

2 

2.2042 

2.2042 

2.2042 

3.8250 

3.5009 

3.1741 

3.1741 

3.1741 

5.5080 

5.0412 


Monoslope 

l 

-4.4733 

-5.7699 

-9.9839 

-4.1492 

-6.4182 

-6.4416 1 

-8.3087 

-14.3768 

-5.9748 

-9.2422 | 


Roof 

2 

1.8801 

1.8801 

1.8801 

3.8250 

3.5009 

2.7073 

2.7073 

2.7073 

5.5080 

5.0412 



1 

-5.0025 

-7.8520 

-10.7016 

-3.4194 

-6.2690 

-7.2036 

-11,3069 

-15.4103 

-4.9240 

-9.0273 


Flat Roof 

2 

NA 

NA 

NA 

3.4194 1 

3.4194 

NA 

NA 

NA 

4.9240 

4.9240 


Gable Roof 

1 

-3.7360 

-6.2690 

-9.4351 

-4.0527 

-6.2690 

-5.3799 

-9.0273 

-13.5866 

-5.8358 

-9.0273 


Mansard Roof 

2 

2.1530 

2.1530 

2.1530 1 

3.7360 

3.4194 

3.1003 

3.1003 

3.1003 

5.3799 

4.9240 

30 


1 

-3.4194 

-5.9524 

-8.8019 

-4.0527 

-6.2690 

-4.9240 

-8.5714 

-12.6747 

-5.8358 

-9.0273 


Hip Roof 

2 

2.1530 

2.1530 

2.1530 

3.7360 

3.4194 

3.1003 

3.1003 

3.1003 

5.3799 

4.9240 1 


Monoslope 

1 

-4.3693 

-5.6357 

-9.7517 

-4.0527 

-6.2690 

-6.2918 

-8.1155 

-14.0425 

-5.8358 

-9.0273 


Roof 

2 

1.8364 

1.8364 

1.8364 

3.7360 

3.4194 

2.6444 

2.6444 

2.6444 

5.3799 

4.9240 



1 

-4.9231 

-7.7274 

-10.5317 

-3.3652 

-6.1695 

-7.0893 

-11.1275 

-15.1656 

-4.8458 

-8.8840 


Flat Roof 

2 

NA 

NA 

NA 

3.3652 

3.3652 

NA 

NA 

NA 

4.8458 

4.8458 


Gable Roof 

1 

-3.6767 

-6.1695 

-9.2853 

-3.9883 

-6.1695 

-5.2945 

-8.8840 

13.3709 

-5.7432 

-8.8840 1 


Mansard Roof 

2 

2.1188 

2.1188 

2.1188 

3.6767 

3.3652 

3.0511 

3.0511 

3.0511 

5.2945 

4.8458 

27 


1 

-3.3652 

-5.8579 

-8.6622 

-3.9883 

-6.1695 

-4.8458 

-8.4353 

-12.4735 

-5.7432 

-8.8840 


Hip Roof 

2 

2.1188 

2.1188 

2.1188 

3.6767 

3.3652 

3.0511 

3.0511 

3.0511 

5.2945 

4.8458 


Monoslope 

1 

-4.2999 

-5.5463 

-9.5969 

-3.9883 

-6.1695 

-6.1919 

-7.9866 

-13.8196 

-5.7432 

-8.8840 


Roof 

2 

1.8072 

1.8072 

1.8072 

3.6767 

3.3652 

2.6024 

2.6024 

2.6024 

5.2945 

4.8458 



1 

-4.8040 

-7.5404 

-10.2769 

-3.2837 

-6.0202 

-6.9178 

-10.8582 

-14.7987 

-4.7286 

-8.6691 


Flat Roof 

2 

NA 

NA 

NA 

3.2837 

3.2837 

NA 

NA 

NA 

4.7286 

4.7286 


Gable Roof 

1 

-3.5878 

-6.0202 

-9.0607 

-3.8918 

-6.0202 

-5.1664 

-8.6691 

-13.0474 

-5.6043 

-8.6691 


Mansard Roof 

2 

2.0675 

2.0675 

2.0675 

3.5878 

3.2837 

2.9773 

2.9773 

2.9773 

5.1664 

4.7286 

24 


1 

-3.2837 

-5.7161 

-8.4526 

-3.8918 

-6.0202 

-4.7286 

-8.2313 

-12.1717 

-5.6043 

-8.6691 


Hip Roof 

2 

2.0675 

2.0675 

2.0675 

3.5878 

3.2837 

2.9773 

2.9773 

2.9773 

5.1664 

4.7286 


Monoslope 

1 

-4.1959 

-5.4121 

-9.3647 

-3.8918 

-6.0202 

-6.0421 

-7.7934 

-13.4852 

-5.6043 

-8.6691 


Roof 

2 

1.7635 

1,7635 

1.7635 

3.5878 

3.2837 

2.5394 

2.5394 

2.5394 

5.1664 

4.7286 



l 

-4.6452 

-7.2912 

-9.9372 

-3.1752 

-5.8212 

-6.6891 

-10.4993 

-14.3095 

-4.5723 

-8.3825 


Flat Roof 

2 

NA 

NA 

NA 

3.1752 

3.1752 

NA 

NA 

NA 

4.5723 

4,5723 


Gable Roof 

1 

-3.4692 

-5.8212 

-8.7612 

-3.7632 

-5.8212 

-4.9956 

-8.3825 

-12.6161 

-5.4190 

-8.3825 


Mansard Roof 

2 

1.9992 

1.9992 

1.9992 

3.4692 

3.1752 

2.8788 

2.8788 

2.8788 

4.9956 

4.5723 

21 


1 

-3.1752 

-5.5272 

-8.1732 

-3.7632 

-5.8212 

-4.5723 

-7.9591 

-11.7694 

-5.4190 

-8.3825 


Hip Roof 

2 

1.9992 

1.9992 

1.9992 

3.4692 

3.1752 

2.8788 

2.8788 

2.8788 

4.9956 

4.5723 


Monoslope 

1 

-4.0572 

-5.2332 

-9.0552 

-3.7632 

-5.8212 

-5.8423 

-7.5358 

-13.0394 

-5.4190 

-8.3825 


Roof 

2 

1.7052 

1.7052 

1.7052 

3.4692 

3.1752 

2.4555 

2.4555 

2.4555 

4.9956 

4.5723 



1 

-4.4864 

-7.0419 

-9.5974 

-3.0666 

-5.6222 

-6.4604 

-10.1403 

-13.8203 

-4.4160 

-8.0959 


Flat Roof 

2 

NA 

NA 

NA 

3.0666 

3.0666 

NA 

NA 

NA 

4.4160 

4.4160 


Gable Roof 

1 

-3.3506 

-5.6222 

-8.4616 

-3.6345 

-5.6222 

-4.8248 

-8.0959 

-12.1848 

-5.2337 

-8.0959 


Mansard Roof 

2 

1.9308 

1,9308 

1.9308 

3.3506 

3.0666 

2.7804 

2.7804 

2.7804 

4.8248 

4.4160 

18 


1 

-3.0666 

-5.3382 

-7.8937 

-3.6345 

-5.6222 

-4.4160 

-7.6870 

-11.3670 

-5.2337 

-8.0959 


Hip Roof 

2 

1.9308 

1.9308 

1.9308 

3.3506 

3.0666 

2.7804 

2.7804 

2.7804 

4.8248 

4.4160 


Monoslope 

1 

-3.9185 

-5.0543 

-8.7456 

-3.6345 

-5.6222 

-5.6426 

-7.2782 

-12.5937 

-5.2337 

-8.0959 


Roof 

2 

| 1.6469 

1.6469 

1.6469 

[ 3.3506 

3.0666 

2.3715 

2.3715 

2.3715 

4.8248 

4.4 160 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 

i 


Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 350 kph, h = 1 8 - 33 m 
Exposure C 


V (kph) 

350 

h (m) 

Roof Form 

Load 

Zone 

Case 

1 

2 

3 

4 

5 


Flat Roof 

1 

-10.0384 

-15.7564 

-21.4745 

-6.8617 

-12.5797 


2 

NA 

NA 

NA 

6.8617 

6.8617 


Gable Roof 

l 

-7.4970 

-12.5797 

18.9331 

-8.1323 

-12.5797 

33 

Mansard Roof 

2 

4.3203 

4.3203 

4.3203 

7.4970 

6.8617 

Hip Roof 

1 

-6.8617 

-11.9444 

-17.6624 

-8.1323 

-12.5797 


2 

4.3203 

4.3203 

4.3203 

7.4970 

6.8617 


Monoslope 

1 

-8.7677 

-11.3090 

-19.5685 

-8.1323 

-12.5797 1 


Roof 

2 

3.6850 

3.6850 

3.6850 

7.4970 

6.8617 


Flat Roof 

1 

-9.8049 

-15.3900 

-20.9751 

-6.7021 

-12.2872 


2 

NA 

NA 

NA 

6.7021 

6.7021 


Gable Roof 

1 

-7.3227 

-12.2872 

-18.4928 

-7.9432 

-12.2872 

30 

Mansard Roof 

2 

4.2198 

4.2198 

4.2198 

7.3227 

6.7021 

Hip Roof 

1 

-6.7021 

-11.6666 

-17.2517 

-7.9432 

-12.2872 


2 

4.2198 

4.2198 

4.2198 

7.3227 

6.7021 


Monoslope 

1 

-8.5638 

-11.0460 

-19.1134 

-7.9432 

-12.2872 


Roof 

2 

3.5993 

3.5993 

3.5993 

7.3227 

6.7021 


Flat Roof 

t 

-9.6493 

-15.1457 

-20.6421 

-6.5957 

-12.0921 


2 

NA 

NA 

NA 

6.5957 

6.5957 


Gable Roof 

1 

-7.2064 

-12.0921 

-18.1993 

-7.8171 

-12.0921 

27 

Mansard Roof 

2 

4.1529 

4.1529 

4,1529 

7.2064 

6.5957 

Hip Roof 

1 

-6.5957 

-11.4814 

-16.9778 

-7.8171 

-12.0921 


2 

4.1529 

4,1529 

4.1529 

7.2064 

6.5957 


Monoslope 

1 

-8.4279 

-10.8707 

-18.8100 

-7.8171 

-12.0921 


Roof 

2 

3.5421 

3.5421 

3.5421 

7.2064 

6.5957 


Flat Roof 

1 

-9.4158 

-14.7793 

-20.1427 

-6.4361 

-11.7996 1 


2 

NA 

NA 

NA 

6.4361 

6.4361 


Gable Roof 

1 

-7.0321 

-11.7996 

-17.7590 

-7.6280 

-11.7996 

24 

Mansard Roof 

2 

4.0524 

4.0524 

4.0524 

7.0321 

6.4361 

Hip Roof 

1 

-6.4361 

-11.2036 

-16.5671 

-7.6280 

-11.7996 


2 

4.0524 

4.0524 

4.0524 

7.0321 

6.4361 


Monoslope 

1 

| -8.2240 

-10.6077 

-18.3549 

-7.6280 

-11.7996 


Roof 

2 

3.4564 

3.4564 

3.4564 

7.0321 

6.4361 


Flat Roof 

1 

-9.1046 

-14.2907 

-19.4768 

-6.2234 

-11.4095 


2 

NA 

NA 

NA 

6.2234 

6.2234 


Gable Roof 

1 

-6.7996 

-11.4095 

-17.1719 

-7.3758 

-11.4095 

21 

Mansard Roof 

2 

3.9184 

3.9184 

3.9184 

6.7996 

6.2234 

Hip Roof 

1 

-6.2234 

-10.8333 

-16.0194 

-7.3758 

-11.4095 


2 

3.9184 

3.9184 

3.9184 

6.7996 

6.2234 


Monoslope 

1 

-7.9521 

-10.2570 

-17.7481 

-7.3758 

-11,4095 


Roof 

2 

3,3422 

3.3422 

3.3422 

6.7996 

6.2234 


Flat Roof 

1 

-8.7933 

-13.8021 

-18.8110 

-6,0106 

*11.0194 


2 

NA 

NA 

NA 

6.0106 

6.0106 


Gable Roof 

1 

-6.5671 

-11.0194 

-16.5848 

-7.1237 

-11.0194 

18 

Mansard Roof 

2 

3.7845 

3.7845 

3.7845 

6.5671 

6.0106 | 

Hip Roof 

1 

-6.0106 

-10.4629 

-15.4717 

-7.1237 

-11.0194 


2 

3.7845 

3.7845 

3.7845 

6.5671 

6.0106 


Monoslope 

1 

-7.6802 

-9.9064 

-17.1414 

-7.1237 

-11.0194 


Roof 

2 

3.2279 

3.2279 

3.2279 

6.5671 

6.0106 


2-151 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-152 CHAPTER 2 - Minimum Design Loads 


Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 150 -200 kph, h = 36 - 48 m 
Exposure C 


V (kph) 

150 

200 

h(m) 

Roof Form 

Load 

Case 

Zone 

Zone 

1 

2 

3 

4 

5 

1 

2 

3 

4 

5 

48 

Flat Roof 

1 

2 

-1.9867 

NA 

-3.1184 

NA 

-4.2501 

NA 

-1.3580 

1.3580 

-2.4897 

1.3580 

-3.5319 

NA 

-5.5438 

NA 

-7.5556 

NA 

-2.4142 

2.4142 

-4.4261 

2.4142 

Gable Roof 
Mansard Roof 

1 

2 

-1.4837 

0.8550 

-2.4897 

0.8550 

-3.7471 

0.8550 

-1.6095 

1.4837 

-2.4897 

1.3580 

-2.6378 

1.5201 

-4.4261 

1.5201 

-6.6615 

1.5201 

-2.8613 

2.6378 

-4.4261 

2.4142 

Hip Roof 

1 

2 

-1.3580 

0.8550 

-2.3639 

0.8550 

-3.4956 

0.8550 

-1.6095 

1.4837 

-2.4897 

1.3580 

-2.4142 

1.5201 

-4.2025 

1.5201 

-6.2144 

1.5201 

-2.8613 

2.6378 

-4.4261 

2.4142 

Monoslope 

Roof 

1 

2 

-1.7352 

0.7293 

-2.2382 

0.7293 

-3.8728 

0.7293 

-1.6095 

1.4837 

-2.4897 

1.3580 

-3.0848 

1.2965 

-3.9790 

1.2965 

-6.8850 

1.2965 

-2.8613 

2.6378 

-4.4261 

2.4142 

45 

Flat Roof 

1 

2 

■1.9724 

NA 

-3.0959 

NA 

-4.2195 

NA 

-1.3482 

1.3482 

-2.4718 

1.3482 

-3.5065 

NA 

-5.5039 

NA 

-7.5013 

NA 

-2.3969 

2.3969 

-4.3942 

2.3969 

Gable Roof 
Mansard Roof 

1 

2 

-1.4731 

0.8489 

-2.4718 

0.8489 

-3.7201 

0.8489 

-1.5979 ! 

1.4731 

-2.4718 

1.3482 

-2.6188 

1.5091 

-4.3942 

1.5091 

-6.6136 

1.5091 

-2.8407 

2.6188 

-4.3942 

2.3969 

Hip Roof 

1 

2 

-1.3482 

0.8489 

-2.3469 

0.8489 

-3.4705 

0.8489 

-1.5979 

1.4731 

-2.4718 

1.3482 

-2.3969 

1.5091 

-4.1723 

1.5091 

-6.1697 

1.5091 

-2.8407 

2.6188 

-4.3942 

2.3969 

Monoslope 

Roof 

1 

2 

-1.7227 

0.7241 

-2.2221 

0.7241 

-3.8450 

0.7241 

-1.5979 

1.4731 

-2.4718 

1.3482 

-3.0627 

1.2872 

-3.9504 

1.2872 

-6.8355 

1.2872 

-2.8407 

2.6188 ' 

-4.3942 

2.3969 

42 

Flat Roof 

1 

2 

-1.9438 

: na 

-3.0511 

NA 

-4.1583 

NA 

-1.3287 

1.3287 

-2.4359 

1.3287 

-3.4557 

NA 

-5.4241 

NA 

-7.3926 

NA 

-2.3621 

2.3621 

-4.3306 

2.3621 

Gable Roof 
Mansard Roof 

1 

2 

H 

-2.4359 

0.8366 

-3.6662 

0.8366 

-1.5747 

1.4517 

-2.4359 

1.3287 

-2.5808 

1.4873 

-4.3306 

1 .4873 

-6.5177 

1.4873 

-2.7996 

2.5808 

-4.3306 

2.3621 

Hip Roof 

1 

2 


-2.3129 

0.8366 


-1.5747 

1.4517 

-2.4359 

1.3287 

-2.3621 

1.4873 

-4.1118 

1.4873 

-6.0803 

1,4873 

-2.7996 

2.5808 

-4.3306 

2.3621 

Monoslope 

Roof 

1 

2 

H88 

| 

-2.1899 

0.7136 

-3.7892 

0.7136 

-1.5747 

1.4517 

-2.4359 

1.3287 

-3.0183 

1.2685 

-3.8931 

1.2685 

-6.7364 

1.2685 

-2.7996 

2.5808 

-4.3306 

2.3621 

39 

Flat Roof 

1 

2 

-1,9152 

NA 

-3.0062 

NA 

-4.0972 

NA 

-1.3092 

1.3092 

-2.4001 

1.3092 

-3.4049 

NA 

-5.3444 

NA 

-7.2839 

NA 

-2.3274 

2.3274 

-4.2669 

2.3274 

Gable Roof 
Mansard Roof 

1 

2 

-1.4304 

0.8243 

-2.4001 

0.8243 

-3.6123 

0.8243 

-1.5516 

1.4304 

-2.4001 

1.3092 

-2.5429 

1 .4654 

-4.2669 

1.4654 

-6.4219 

1.4654 

-2.7584 

2.5429 

-4.2669 

2.3274 

Hip Roof 

1 

2 

-1.3092 

0.8243 

-2.2789 

0.8243 

-3.3699 

0,8243 

-1.5516 

1.4304 

-2.4001 

1.3092 

-2.3274 

1.4654 

-4.0514 

1.4654 

-5.9909 

1.4654 

-2.7584 

2.5429 

-4.2669 

2.3274 

Monoslope 

Roof 

1 

2 

-1.6728 

0.7031 

-2.1577 

0.7031 

-3.7335 

0.7031 

-1.5516 

1.4304 

-2.4001 

1.3092 

-2.9739 

1.2499 

-3.8359 

1.2499 

-6.6374 

1.2499 

-2.7584 

2.5429 

-4.2669 

2.3274 

36 

Flat Roof 

1 

2 

-1.8724 

NA 

-2.9389 

NA 

-4.0054 

NA 

-1.2798 

1.2798 

-2.3464 

1.2798 

-3.3287 

NA 

-5.2247 

NA 

-7.1208 

NA 

-2.2753 

2.2753 

-4.1713 

2.2753 

Gable Roof 
Mansard Roof 

1 

2 

-1.3984 

0.8058 

-2.3464 

0.8058 

-3.5314 

0.8058 

-1.5169 

1.3984 

-2.3464 

1.2798 

-2.4860 

1 .4326 

-4.1713 

1.4326 

-6.2781 

1.4326 

-2.6966 

2.4860 

-4.1713 

2.2753 

Hip Roof 

1 

2 

-1.2798 

0.8058 

-2.2279 

0.8058 

-3.2944 

0.8058 

-1.5169 

1.3984 

-2.3464 

1.2798 

-2.2753 

1.4326 

-3.9607 

1.4326 

-5.8567 

1.4326 

-2.6966 

2.4860 

-4.1713 

2.2753 

Monoslope 

Roof 

1 

2 

-1.6354 

0.6873 

-2.1094 

0.6873 

-3.6499 

0.6873 

-1.5169 

1.3984 

-2.3464 

1.2798 

‘2.9073 

1.2219 

-3.7500 

1.2219 

-6.4888 

1.2219 

-2.6966 

2.4860 

-4.1713 

2,2753 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-153 


Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 250 -300 kph, h = 36 - 48 m 
Exposure C 


V (kph) 

250 

300 

h (m) 

Roof Form 

Load 

Zone 

Zone 

Case 

1 

2 

3 

4 

5 

1 

2 

3 

4 

5 


Flat Roof 

r 

-5.5 1 86 

-8.6622 

-11.8057 

-3.7722 

-6.9158 

-7.9468 

-12.4735 

■17.0002 

-5.4320 

-9.9587 


2 

NA 

NA 

NA 

3.7722 

3.7722 

NA 

NA 

NA 

5 4320 

5.4320 


Gable Roof 

! 

-4.1215 

-6.9158 

-10.4086 

-4.4708 

-6.9158 

-5.9350 

-9.9587 

-14.9883 

-6.4379 

-9.9587 

48 

Mansard Roof 

2 

2.3751 

2.3751 

2.3751 

4.1215 

3.7722 

3.4202 

3.4202 

3.4202 

5.9350 

5.4320 

Hip Roof 

t 

-3.7722 

-6.5665 

-9.7100 

-4.4708 

-6.9158 

-5.4320 

-9.4557 

-13.9824 

-6.4379 

-9.9587 


2 

2.3751 

2.3751 

2.3751 

4.1215 

3.7722 

3.4202 

3.4202 

3.4202 

5.9350 

5.4320 


Monoslope 

1 

-4.8201 

-6.2172 

-10.7579 

-4.4708 

-6.9158 

-6.9409 

-8.9528 

-15.4913 

-6.4379 

-9.9587 


Roof 

2 

2.0258 

2.0258 

2.0258 

4.1215 

3.7722 

2.9172 

2.9172 

2.9172 

5.9350 

5.4320 


Flat Roof 

1 

-5.4789 

-8.5998 

-11.7208 

-3.7451 

-6.8660 

-7.8897 

-12.3838 

-16.8779 

-5.3929 

-9.8871 


2 

NA 

NA 

NA 

3.7451 

3.7451 

NA 

NA 

NA 

5.3929 

5.3929 


Gable Roof 

l 

-4.0919 

-6.8660 

-10.3337 

-4.4386 

-6.8660 

-5.8923 

-9.8871 

-14.8805 

-6.3916 

-9.8871 

45 

Mansard Roof 

2 

2.3580 

2.3580 

2.3580 

4.0919 

3.7451 

3.3956 

3.3956 

3.3956 

5.8923 

5.3929 

Hip Roof 

1 

-3.7451 

-6.5192 

-9.6402 

-4.4386 

-6.8660 

-5.3929 

-9.3877 

-13.8818 

-6.3916 

-9.8871 


2 

2.3580 

2.3580 

2.3580 

4.0919 

3.7451 

3.3956 

3.3956 

3.3956 

5.8923 

5.3929 


Monoslope 

t 

-4.7854 

-6.1725 

-10.6805 

-4.4386 

-6.8660 

-6.8910 

-8.8884 

-15.3799 

-6.3916 

-9.8871 


Roof 

2 

2.0113 

2.0113 

2.0113 

4.0919 

3.7451 

2.8962 

2.8962 

2.8962 

5.8923 

5.3929 


Flat Roof 

1 

-5.3995 

-8.4752 

-11.5509 

-3.6908 

-6.7665 

-7.7753 

-12.2043 

-16.6333 

-5.3148 

-9.7438 


2 

NA 

NA 

NA 

3.6908 

3.6908 

NA 

NA 

NA 

5.3148 

5.3148 


Gable Roof 

1 

-4.0326 

-6.7665 

-10.1839 

-4.3743 

-6.7665 

-5.8069 

-9.7438 

-14.6649 

-6.2990 

-9.7438 

42 

Mansard Roof 

2 

2.3238 

2.3238 

2.3238 

4.0326 

3.6908 

3.3463 

3.3463 

3.3463 

5.8069 

5.3148 

Hip Roof 

1 

-3.6908 

-6.4248 

-9.5004 

-4.3743 

-6.7665 

-5.3148 

-9.2517 

-13.6806 

-6.2990 

-9.7438 


2 

2.3238 

2.3238 

2.3238 

4.0326 

3.6908 

3.3463 

3.3463 

3.3463 

5.8069 

5.3148 


Monoslope 

1 

-4.7160 

-6.0830 

-10.5257 

-4.3743 

-6.7665 

-6.7911 

-8.7595 

-15.1570 

-6.2990 

-9.7438 


Roof 

2 

1.9821 

1.9821 

1.9821 

4.0326 

3.6908 

2.8542 

2.8542 

2.8542 

5.8069 

5.3148 


Flat Roof 

1 

-5.3201 

-8.3506 

-11.3810 

-3.6365 

-6.6670 

-7.6610 

-12.0248 

-16.3887 

-5.2366 

-9.6005 


2 

NA 

NA 

NA 

3.6365 

3.6365 

NA 

NA 

NA 

5.2366 

5.2366 


Gable Roof 

1 

-3.9733 

-6.6670 

-10.0342 

-4.3100 

-6.6670 

-5.7215 

-9.6005 

-14.4492 

-6.2064 

-9.6005 

IQ 

Mansard Roof 

2 

2.2897 

2.2897 

2.2897 

3.9733 

3.6365 

3.2971 

3.2971 

3.2971 

5.7215 

5.2366 

J7 

Hip Roof 

1 

-3.6365 

-6.3303 

-9.3607 

-4.3100 

-6.6670 

-5.2366 

-9.1156 

-13.4794 

-6.2064 

-9.6005 


2 

2.2897 

2.2897 

2.2897 

3.9733 

3.6365 

3.2971 

3.2971 

3.2971 

5.7215 

5.2366 


Monoslope 

1 

-4.6467 

-5.9936 

-10.3709 

-4.3100 

-6.6670 

-6.6912 

-8.6307 

-14.9341 

-6.2064 

-9.6005 


Roof 

2 

1.9530 

1.9530 

1.9530 

3.9733 

3.6365 

2.8123 

2.8123 

2.8123 

5.7215 

5.2366 


Flat Roof 

l 

-5.2010 

-8.1636 

-11.1262 

-3.5551 

-6.5177 

-7.4895 

-11.7556 

-16.0218 

-5.1194 

-9.3855 


2 

NA 

NA 

NA 

3.5551 

3.5551 

NA 

NA 

NA 

5.1194 

5.1194 


Gable Roof 

1 

-3.8843 

-6.5177 

-9.8095 

-4.2135 

-6.5177 

-5.5934 

-9.3855 

-14.1257 

-6.0674 

-9.3855 

36 

Mansard Roof 

2 

2.2384 

2.2384 

2.2384 

3.8843 

3.5551 

3.2233 

3.2233 

3.2233 

5.5934 

5.1194 

Hip Roof 

1 

-3.5551 

-6.1886 

-9.1512 

-4.2135 

-6.5177 

-5.1194 

-8.9115 

-13.1777 

-6.0674 

-9.3855 


2 

2.2384 

2.2384 

2.2384 

3.8843 

3.5551 

3.2233 

3.2233 

3.2233 

5.5934 

5.1194 


Monoslope 

1 

-4.5427 

-5.8594 

-10.1387 

-4.2135 

-6.5177 

-6.5414 

-8.4375 

-14.5997 

-6.0674 

-9,3855 


Roof 

2 

1.9092 

1.9092 

1.9092 

3.8843 

3.5551 

2.7493 

2.7493 

2.7493 

5.5934 

5.1194 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-154 CHAPTER 2 - Minimum Design Loads 

» 


Table 207E.7-2 

Components and Cladding - Part 4 
C&C, V = 350 kph, h = 36 - 48 m 
Exposure C 


V (kph) 

350 

h(m) 

Roof Form 

Load 

Case 

Zone 

1 

2 

3 

4 

5 

48 

Flat Roof 

1 

2 

-10.8165 

NA 

-16.9778 

NA 

-23.1392 

NA 

-7.3936 

7.3936 

-13.5549 

7.3936 

Gable Roof 
Mansard Roof 

1 

2 

-8.0782 

4.6552 

-13.5549 

4.6552 

-20.4008 

4.6552 

-8.7628 

8.0782 

-13.5549 

7.3936 

Hip Roof 

1 

2 

-7.3936 

4.6552 

-12.8703 

4.6552 

-19.0316 

4.6552 

-8.7628 

8.0782 

-13.5549 

7.3936 

Monoslope Roof 

1 

2 

-9.4474 

3.9706 

-12.1857 

3.9706 

-21.0854 

3.9706 

-8.7628 

8.0782 

-13.5549 

7.3936 

45 

Flat Roof 

1 

2 

-10.7387 

NA 

-16.8557 

NA 

-22.9727 

NA 

-7.3404 

7.3404 

-13.4574 

7.3404 

Gable Roof 
Mansard Roof 

1 

2 

-8.0201 

4.6217 

-13.4574 

4.6217 

-20.2540 

4.6217 

-8.6997 

8.0201 

-13.4574 

7.3404 

Hip Roof 

1 

2 

-7.3404 

4.6217 

-12.7777 

4.6217 

-18.8947 

4.6217 

-8.6997 

8.0201 

-13.4574 ' 
7.3404 

Monoslope Roof 

1 

2 

-9.3794 

3.9421 

-12.0980 

3.9421 

-20.9337 

3.9421 

-8.6997 

8.0201 

-13.4574 

7.3404 

42 

Flat Roof 

1 

2 

-10.5831 

NA 

-16.6114 ! 
NA 

-22.6398 

NA 

-7.2340 

7.2340 

-13.2623 

7.2340 

Gable Roof 
Mansard Roof 

1 

2 

-7.9038 

4.5547 

-13.2623 

4.5547 

-19.9605 

4.5547 

-8.5736 

7.9038 

-13.2623 

7.2340 

Hip Roof 

1 

2 

-7.2340 

4.5547 

-12.5925 

4.5547 

-18.6209 

4.5547 

-8.5736 

7.9038 

-13.2623 

7.2340 

Monoslope Roof 

1 

2 

-9.2435 

3.8849 

-11.9227 

3.8849 

-20.6303 

3.8849 

-8.5736 

7.9038 

-13.2623 

7.2340 

39 

Flat Roof 

1 

2 

-10.4274 

NA 

-16.3671 

NA 

-22.3068 

NA 

-7.1276 

7.1276 

-13.0673 

7.1276 

Gable Roof 
Mansard Roof 

1 

2 

-7.7876 

4.4878 

-13.0673 

4.4878 

-19.6670 

4.4878 

-8.4476 

7.7876 

-13.0673 

7.1276 

Hip Roof 

1 

2 

-7.1276 

4.4878 

-12.4073 

4.4878 

-18.3470 

4.4878 

-8.4476 

7.7876 

-13.0673 

7.1276 

Monoslope Roof 

1 

2 

-9.1075 

3.8278 

*1 1.7474 

3.8278 

-20.3269 

3.8278 

-8.4476 

7.7876 

-13.0673 

7.1276 

36 

Flat Roof 

t 

2 

-10.1940 

NA 

-16.0007 

NA 

-21.8074 

NA 

-6.9680 

6.9680 

-12.7748 

6.9680 

Gable Roof 
Mansard Roof 

1 

2 

-7.6132 

4.3873 

-12.7748 

4.3873 

-19.2267 

4.3873 

-8.2584 

7.6132 

-12.7748 

6.9680 

Hip Roof 

1 

2 

-6.9680 

4.3873 

-12,1296 

4.3873 

-17.9363 

4.3873 

-8.2584 

7.6132 

-12.7748 

6.9680 

Monoslope Roof 

1 

2 

-8.9036 

3.7421 

-11.4844 

3.7421 

-19.8718 

3.7421 

-8.2584 

7.6132 

-12.7748 

6.9680 


Association of Structural Engineers of the Philippines, Inc, (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-155 


Part 5: Open Buildings 

Commentary: 

In determining loads on component and cladding elements 
for open building roofs using Figures 207 E. 8-1, 207 E. 8-2 
and 2 07 E. 8-3, it is important for the designer to note that 
the net pressure coefficient C N is based on contributions 
from the top and bottom surfaces of the roof This implies 
that the element receives load from both surfaces. Such 
would not be the case if the surface below the roof were 
separated structurally from the top roof surface. In this 
case, the pressure coefficient should be separated for the 
effect of top and bottom pressures, or conservatively, each 
surface could be designed using the C N value from Figures 
207E.8-1, 207E.8-2 and207E.8-3. 

207E.8 Building Types 

The provisions of Section 207E.8 are applicable to an open 
building of all heights having a pitched free roof, 
monosloped free roof, or troughed free roof The steps 
required for the determination of wind loads on 
components and cladding for these building types is shown 
in Table 207E.8-1. 

207E.8.1 Conditions 

For the determination of the design wind pressures on 
components and claddings using the provisions of Section 
207E.8.2, the conditions indicated on the selected figure(s) 
shall be applicable to the building under consideration. 

207E.8.2 Design Wind Pressures 

The net design wind pressure for component and cladding 
elements of open buildings of all heights with monoslope, 
pitched, and troughed roofs shall be determined by the 
following equation: 

p = q h GC N (207E.8-1) 

where 

q h = velocity pressure evaluated at mean roof 
height h using the exposure as defined in 
Section 207A.7.3 that results in the highest 
wind loads for any wind direction at the site 
G = gust-effect factor from Section 207A.9 
C N = net pressure coefficient given in: 

• Figure 207E.8-1 for monosloped roof 

• Figure 207E.8-2 for pitched roof 

• Figure 207E.8-3 for troughed roof 


Net pressure coefficients C N include contributions from top 
and bottom surfaces. All load cases shown for each roof 
angle shall be investigated. Plus and minus signs signify 
pressure acting toward and away from the top surface of 
the roof, respectively. 


User Note: 

Use Part 5 of Section 207 E for determining wind 
pressures for C&C of open buildings having pitched, 
monoslope or troughed roofs . These provisions are 
based on the Directional Procedure with wind pressures 
calculated from the specified equation applicable to 
each roof surface. 


Table 207E.8-1 

Steps to Determine C&C Wind Loads 
Open Buildings 


Step 1: Determine risk category, see Table 103-1 

Step 2: Determine the basic wind speed, V, for the 
applicable risk category, see Figure 207A.5- 
1A, BorC 

Step 3: Determine wind load parameters: 

> Wind directionality factor K zt , 
see Section 207 A.6 and Table 207A.6-1 

> Exposure category B, C or D, see Section 
207A.7 

> Topographic factor K zt9 see Section 
207A.8 and Figure 207A.8-1 

> Gust effect factor, G, see Section 207A.9 

Step 4 : Determine velocity pressure exposure 
coefficient, K z or K h , see Table 207E.3-1 

Step 5: Determine velocity pressure, q h , 

see Equation 207E.3-1 

Step 6: Determine net pressure coefficients, C N 

> Monosloped roof, see Figure 207E.8-1 

> Pitched roof, see Figure 207E.8-2 

> Troughed roof, see Figure 207E.8-3 

Step 7 : Calculate wind pressure, p, see Equation 
207E.8-1 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-156 CHAPTER 2 - Minimum Design Loads 


Part 6: Building Appurtenances and Rooftop 

Structures and Equipment 

207E.9 Parapets 

The design wind pressure for component and cladding 
elements of parapets for all building types and heights, 
except enclosed buildings with ft < 48 m for which the 
provisions of Part 4 are used, shall be determined from the 
following equation: 

p = q p [(GC p ) - ( GC pi )] (207E.9-1) 

where 

q p = velocity pressure evaluated at the top of the 
parapet 

(GC p ) = external pressure coefficient given in 

• Figure 207E.4-1 for walls with ft > 18 m 

• Figures 207 E. 4-2 A to 207E.4-2C for flat 
roofs, gable roofs, and hip roofs 

• Figure 207E.4-3 for stepped roofs 

• Figure 207E.4-4 for multispan gable roofs 

• Figure 207E.4-5A and 207E.4-5B for 
monoslope roofs 

• Figure 207E.4-6 for sawtooth roofs 

• Figure 207E.4-7 for domed roofs of all 
heights 

• Figure 207E.6-1 for walls and flat roofs 
with ft > 18 m 

• Figure 207B.4-3 for footnote 4 for arched 
roofs 

(GCpj) = internal pressure coefficient from 
Table 207 A. 1 1-1, based on the porosity of the 
parapet envelope 


* Load Case B: Leeward Parapet shall consist of 
applying the applicable positive wall pressure from 
Figure 207E.4-1 (ft < 18 m) or Figure 207E.6-1 
(ft > 18 m) to the windward surface of the parapet, 
and applying the applicable negative wall pressure 
from Figure 207E.4-1 (ft < 18 m) or Figure 207E.6-1 
(ft > 18 m) as applicable to the leeward surface. Edge 
and comer zones shall be arranged as shown in the 
applicable figures. ( GC p ) shall be determined for 
appropriate roof angle and effective wind area from 
the applicable figures. 

If internal pressure is present, both load cases should be 
evaluated under positive and negative internal pressure. 

The steps required for the determination of wind loads on 
component and cladding of parapets are shown in Table 
207E.9-1. 


User Note: 

Use Part 6 of Section 207E for determining wind 
pressures for C&C on roof overhangs and parapets of 
buildings. These provisions are based on the 
Directional Procedure with wind pressures calculated 
from the specified equation applicable to each roof 
overhang or parapet surface. 


Two load cases, see Figure 207E.9-1, shall be considered: 

• Load Case A: Windward Parapet shall consist of 
applying the applicable positive wall pressure from 
Figure 207E.4-1 (ft < 18 m) or Figure 207E.6-1 
(ft > 18 m) to the windward surface of the parapet 
while applying the applicable negative edge or comer 
zone roof pressure from Figures 207E.4-2 (A, B or C), 
207E.4-3, 207E.4-4, 207E.4-5 (A or B), 207E.4-6, 
207E.4-7, Figure 207B.4-3 footnote 4, or Figure 
207E.6-1 (ft > 18 m) as applicable to the leeward 
surface of the parapet. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-157 


Table 207E.9-1 

Steps to Determine C&C Wind Loads 
Parapets 


Step 1: Determine risk category, see Table 103-1 

Step 2: Determine the basic wind speed, V, for the 
applicable risk category, see Figure 207A.5- 
1A, B or C 

Step 3: Determine wind load parameters: 

> Wind directionality factor K zt , 
see Section 207A.6 and Table 207A.6-1 

> Exposure category B, C or D, see Section 
207A.7 

> Topographic factor K zt , see Section 
207A.8 and Figure 207A.8-1 

> Enclosure classification, see Section 
207 A. 10 

> Internal pressure coefficient, (GC p j), see 
Section 207A.11 and Table 207A.11-1 

Step 4: Determine velocity pressure exposure 
coefficient, K h , at the top of the parapet see 
Table 207E.3-1 

Step 5: Determine velocity pressure, q p , at the top of 
the parapet, see Equation 207E.3-1 

Step 6: Determine external pressure coefficient for 
wall and roof surfaces adjacent to parapet, 
(GC P ) 

> Walls with h < 18 m, see Figure 207E.4- 
1 

> Flat, gable and hip roofs, see Figures 
207E.4-2A to 207E.4.2C 

> Stepped roofs, see Figure 207E.4-3 

> Multispan gable roofs, see Figure 
207E.4-4 

> Monoslope roofs. Figures 207E.4-5A and 
207E.4-5B 

> Sawtooth roofs, see Figure 207E.4-6 

> Domed roofs of all heights, see Figure 
207E.4-7 

> Walls and flat roofs with h > 18 m, see 
Figure 207E.6-1 

> Arched roofs, see footnote 4 of Figure 
207B.4-3 

Step 7: Calculate wind pressure, p, see Equation 
207E.9-1 on windward and leeward face of 
parapet, considering two load cases (Case A 
and Case B) as shown in Figure 207E.9-1 


207E.10 Roof Overhangs 

The design wind pressure for roof overhangs of enclosed 
and partially enclosed buildings of all heights, except 
enclosed buildings with h < 48 m for which the provisions 
of Part 4 are used, shall be determined from the following 
equation: 


p = q h [(GC p ) - (GC pi )] (N/m 2 ) (207E.10-1) 


where 

Rh 


(GC P ) 


(GC P i) 


velocity pressure from Section 207E.3.2 
evaluated at mean roof height h using 
exposure defined in Section 207A.7.3 
external pressure coefficients for overhangs 
given in Figures 207E.4-2A to 207E.4-2C (flat 
roofs, gable roofs, and hip roofs), including 
contributions from top and bottom surfaces of 
overhang. The external pressure coefficient 
for the covering on the underside of the roof 
overhang is the same as the external pressure 
coefficient on the adjacent wall surface, 
adjusted for effective wind area, determined 
from Figure 207E.4-1 or Figure 207E.6-1 as 
applicable 

internal pressure coefficient given in 
Table 207A.11-1 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-158 CHAPTER 2 - Minimum Design Loads 


The steps required for the determination of wind loads on 
components and cladding of roof overhangs are shown in 
Table 207E.10-1. 


Table 207E.10-1 

Steps to Determine C&C Wind Loads 
Roof Overhangs 


Step 1: 

Determine risk category, see Table 103-1 

Step 2; 

Determine the basic wind speed, V, for the 
applicable risk category, see Figure 207A.5- 
1A, B or C 

Step 3 : 

Determine wind load parameters: 


> Wind directionality factor K zt , 

see Section 207A.6 and Table 207A.6-1 


> Exposure category B, C or D, see Section 
207A.7 


> Topographic factor ff zt , see Section 
207 A.8 and Figure 207A.8-1 


> Enclosure classification, see Section 
207A.10 


> Internal pressure coefficient, ( GC pi ), 
see Section 207 A. 11 and 

Table 207A.11-1 

Step 4: 

Determine velocity pressure exposure 
coefficient, K h , see Table 207E.3-1 

Step 5: 

Determine velocity pressure, q h , at mean roof 
height h using Equation 207E.3-1 

Step 6: 

Determine external pressure coefficient, 
(GC p ), using Figures 207E.4-2A through C 
for flat, gabled and hip roofs 

Step 7: 

Calculate wind pressure, p, using 
Equation 207E. 10-1, refer to 

Figure 207E.10-1 


207E.11 Rooftop Structures and Equipment for 
Buildings with h < 18 m 

The components and cladding pressure on each wall of the 
rooftop structure shall be equal to the lateral force 
determined in accordance with Section 207D.5.1 divided 
by the respective wall surface are of the rooftop structure 
and shall be considered to act inward and outward. The 
components and cladding pressure on the roof shall be 
equal to the vertical uplift force determined in accordance 
with Section 207D.5.1 divided by the horizontal projected 
area of the roof of the rooftop structure and shall be 
considered to act in the upward direction. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-159 

# 




-1.4 


- 1.1 


- 0.8 


+0.7 

+ 1.0 


Notes: 

1. Vertical scale denotes GC p to be used with q h . 

2. Horizontal scale denotes effective wind area, m 2 . 

3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

4. Each component shall be designed for maximum positive and negative pressures. 

5. Values of GC p for walls shall be reduced by 10% when 0 < 10° . 

6. Notation: 

a = 1 0% of least horizontal dimension or 0. 4ft, whichever is smaller, but not less than either 4% of least horizontal dimension or 0.9 m. 

ft - mean roof height, m, except that eave height shall be used for 9 < 10 ° . 

0 = angle of plane of roof from horizontal, ° 


Figure 207E.4-1 

External Pressure Coefficients, GC p Walls, h < 18 m Enclosed 
Partially Enclosed Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-160 CHAPTER 2 - Minimum Design Loads 



u 

o 


CD 


O 

<-W 

<D 

o 

O 


0) 


c/1 

c/i 

CD 

5m 

PH 


0.1 


0.9 1.9 4.6 9.3 

Effective Wind Area, nf 


18.6 
2 


46.5 92.9 


cd 


CD 

XI 

W 



-u 


-01 


0.1 


0.9 1.9 4.6 9.3 18.6 46.5 92.9 


Notes: 


Effective Wind Area, m 2 


1. 

2 . 

3. 

4. 

5. 


Vertical scale denotes GC P to be used with q *. 


Horizontal scale denotes effective wind area, m . 

Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

Each component shall be designed for maximum positive and negative pressures. 

If a parapet equal to or higher than 0.9 m is provided around the perimeter of the roof with 0 <7° , the negative values of GC p in Zone 3 shall be equal 
to those for Zone 2 and positive values of GC p in Zones 2 and 3 shall be set equal to those for wall Zones 4 and 5 respectively in Figure 207E.4-1. 


6 . 

7. 


Values of GC P for roof overhangs include pressure contributions from both upper and lower surfaces. 


Notation: 


10% of least horizontal dimension or 0. 4 h, whichever is smaller, but not less than either 4% of least horizontal dimension or 0.9 m. 
eave height shall be used for 9 < 10 ° . 
angle of plane of roof from horizontal, 0 


Figure 207E.4-2A 

External Pressure Coefficients, GC p Gable Roofs 6 < 7°, h < 18 m 
Enclosed, Partially Enclosed Buildings 


L 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-161 



Notes: 


Qh 

U 

O 


<D 

* i-H 

o 

4h 

D 

o 

O 

CD 

c/) 

CZ) 

CD 

i-H 

Pm 

13 


<D 

x 

w 


CM 


U 


O 




<D 

■ t-H 

O 


4h 

CD 


O 

O 


CD 

P 


C/3 

cn 


CD 


PM 


e 


CD 


X 

w 



0 l 0.9 1.9 4.6 9.3 18.6 46.5 92.9 


Effective Wind Area, m 2 



0.1 0.9 1.9 4.6 9.3 18.6 46.5 92.9 


Effective Wind Area, m 2 


1. Vertical scale denotes GC p to be used with q h . 

2. Horizontal scale denotes effective wind area, m 2 . 

3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

4. Each component shall be designed for maximum positive and negative pressures. 

5. Values of GC p for roof overhangs include pressure contributions from both upper and lower surfaces. 

6. For hip roofs with 7 < 8 < 27°, edge/ridge strips and pressure coefficients for ridges of gabled roofs shall apply on each hip. 

7. For hip roofs with 0 < 25 °, Zone 3 shall be treated as Zone 2. 

8. Notation: 

A =10% of least horizontal dimension or 0. 4h, whichever is smaller, but not less than either 4% of least horizontal dimension 0.9 m. 

h ~ mean roof height, m, except that eave height shall be used for 0 < 10 ° . 

9 = angle of plane of roof from horizontal, ° 


Figure 207E.4-2B 

External Pressure Coefficients, GC p Gable/Hip Roofs 7° < 6 < 27°, h < 18 m 
Enclosed, Partially Enclosed Buildings 

National Structural Code of the Philippines Volume I, 7th Edition, 2015 




2-162 CHAPTER 2 - Minimum Design Loads 


®& 3 ) 


Effective Wind Area, m 2 


Overhang 


Effective Wind Area, m 2 


Notes: 


Vertical scale denotes GC p to be used with q h . 

Horizontal scale denotes effective wind area, m 2 

Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

Each component shall be designed for maximum positive and negative pressures. 

Values of GC p for roof overhangs include pressure contributions from both upper and lower surfaces. 

Notation: 

a = 1 0% of least horizontal dimension or 0 . 4 h, whichever is smaller, but not less than either 4% of least horizontal dimension 0 9 

h = mean roof height, m 

6 — angle of plane of roof from horizontal, ° 

Figure 207E.4-2C 

External Pressure Coefficients, GC p Gable Roofs 27° < 6 < 45°, ft < 18 m 
Enclosed, Partially Enclosed Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




1 





Roof 












































r — 1 















— ■ 

— ■ 

— 

— 

— 







CHAPTER 2 - Minimum Design Loads 2-163 


h x > 3 m 
b = 1.5/h 
b < 30 m 


hi 

— = 0.30 to 0.70 
h 

0.25 to 0.75 
w 


Notes: 




I On the lower level of flat, stepped roofs shown in Figure 207E.4-3, the zone designations and pressure coefficients shown in Figure 207E.4-2A shall 
apply, except that at the roof-upper wall intersection(s), Zone 3 shall be treated as Zone 2 and Zone 2 shall be treated as Zone 1 . Positive values of GC V 
equal to those for walls in Figure 207E.4-1 shall apply on the cross-hatched areas shown in Figure 207E.4-3, 

2. Notation: 

b =1. 5/ii in Figure 207E.4-3, but not greater than 30 m. 
h = mean roof height, m 

h t = hi or h 2 in Figure 207E.4-3; h = + h 2 \ >3.1 m; hrfh = 0. 3 to 0. 7. 

W = Building width in Figure 207E.4-3. 

W t = Wx or W 2 or W 3 in Figure 207E.4-3. W = W 1 + W 2 orW 1 + W 2 + W 3 ; WJW = 0. 25 to 0. 75. 

0 = Angle of plane of roof from horizontal, ° 

Figure 207E.4-3 

External Pressure Coefficients, GC p Stepped Roofs, h < 18 m 
Enclosed, Partially Enclosed Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-164 CHAPTER 2 - Minimum Design Loads 



-3.0 

- 2.8 

_ - 2.6 
Ph 

O -2-4 

O -2-2 


- 2.0 

- 1.8 

- 1.6 


P 
• Sh 

O 

o -> 2 
U-i.o 
£ - 0.8 
3 

C/3 
8 -°- 4 
£ - 0 - 2 

-a o 

e +o - 2 

(D +0.4 
X! +0.6 

^ + 0.8 
0.1 


- 0.6 


(3) 










\ 

l 

10 c 

< 6 

S 30° 

— 

© 


V 







A 







. 

N 





































































^TX2)^3'I 

— 

— ~ 

\ 

— 


— 




_ 






0.9 1.9 


4.6 9.3 18.6 46.5 92.9 


Effective Wind Area, m 2 

1. Vertical scale denotes GC p to be used with q h . 



0.1 


0.9 1.9 4.6 


2 . 

3. 

4. 

5. 

6 . 


Horizontal scale denotes effective wind area A, m 2 


9.3 18.6 

2 


46.5 92.9 


Effective Wind Aros m 

Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. ? 

Each component shall be designed for maximum positive and negative pressures. 

For 0 < 10°, values of GC p from Figure 207E.4-2A shall be used. 

Notation: 


a = 1 0% of least horizontal dimension or 0. 4 h, whichever is smaller, but not less than either 4% of least horizontal dimension or 0.9 m. 

h = mean roof height, m, except that the eave height shall be used for 0 < 10 ° 

W = building module width, m 

0 = angle of plane of roof from horizontal, ° 


Figure 207E.4-4 

External Pressure Coefficients, GC p Multispan Gable Roofs, h < 18 m 
Enclosed, Partially Enclosed Buildings 

Association of Structural Engineers of the Philippines, Inc. (ASEP) 





CHAPTER 2 - Minimum Design Loads 2-165 


r 2o i 


pi 





0.1 


0.9 1.9 


Effective Wind Area, m 2 



- 2.6 


- 1.8 

- 1.6 
-I 5 

-1.3 

- 1.2 

- 1.1 


+0 2 
+0.3 


4.6 9.3 18.6 46.5 92.9 


Notes: 

1 . Vertical scale denotes GC p to be used with q h . 

2. Horizontal scale denotes effective wind area A, m 2 

3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

4. Each component shall be designed for maximum positive and negative pressures. 

5. For 6 < 3°, values of GC p from Figure 207E.4-2A shall be used. 

6. Notation: 

a - 10% of least horizontal dimension or 0.4fc, whichever is smaller, but not less than either 4% of least horizontal dimension or 0.9 m. 

h = eave height shall be used for 0 < 10° 

W = building width, m 
6 - angle of plane of roof from horizontal, ° 


Figure 207E.4-5A 

External Pressure Coefficients, GC p Monoslope Roofs, 3° < 6 < 10 °, h < 18 m 
Enclosed, Partially Enclosed Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-166 CHAPTER 2 - Minimum Design Loads 



Notes: 

1 . Vertical scale denotes GC p to be used with q h . 

2. Horizontal scale denotes effective wind area A , m 2 

3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

4. Each component shall be designed for maximum positive and negative pressures. 

5. Notation: 

a = 10% of least horizontal dimension or 0. 4 h, whichever is smaller, but not less than either 4% of least horizontal dimension 0.9 m 

h = mean roof height, m 

W = building width, m 

0 = angle of plane of roof from horizontal, ° 


Figure 207E.4-5B 

External Pressure Coefficients, GC p Monoslope Roofs, 10° < 0 < 30°, h < 18 m 
Enclosed, Partially Enclosed Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



I _ tv 

m 


CHAPTER 2 - Minimum Design Loads 


2-167 



1. Vertical scale denotes GC p to be used with q h . 

2. Horizontal scale denotes effective wind area A , m 2 

3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

4. Each component shall be designed for maximum positive and negative pressures. 

5. For 6 < 10°, values of GC p from Figure 207E.4-2A shall be used. 

6. Notation: 

a = 10% of least horizontal dimension or 0. Ah, whichever is smaller, but not less than either 4% of least horizontal dimension or 0.9 m. 

h = mean roof height, m, except that the eave height shall be used for 0 < 10° 

W = building module width, m 

6 = angle of plane of roof from horizontal, ° 


Figure 207E.4-6 

External Pressure Coefficients, GC p Sawtooth Roofs, h < 18 m 
Enclosed, Partially Enclosed Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 




2-168 CHAPTER 2 - Minimum Design Loads 



External Pressure Coefficient for Domes with a Circular Base 

9 , degrees 

Negative Pressures 

Positive Pressures 

Positive Pressures 

0-90 

0-60 

61-90 

GCp 

-0.90 

+0.90 

+0.50 


Notes: 

1 . Values denote GC p to be used with g (/li)+/) , where h D + / is the height at the top of the dome. 

2. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

3. Each component shall be designed for maximum positive and negative pressures. 

4. Values apply to 0 < h D /D < 0 . 5 , 0 . 2 < f/D < 0 . 5 . 

5. 0 = 0 ° on dome springline, 9 = 90 ° at dome center top point. / is measured from spring line to top. 

Figure 207E.4-7 

External Pressure Coefficients, GC p Doomed Roofs, All Heights 
Enclosed, Partially Enclosed Buildings and Structures 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




CHAPTER 2 - Minimum Design Loads 2-169 




I I Interior Zones End Zones ^HCorner Zones 

Roofs - Zone 1/Walls - Zone 4 Roofs - Zone 2/Walls - Zone 5 Roofs - Zone 3 


Notes: 

1 . Pressures shown are applied normal to the surface, for exposure B, at h = 9 m. Adjust to other conditions using Equation 207E.5- 1 . 

2. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 

3. For hip roofs with 0 < 25°, Zone 3 shall be treated as Zone 2. 

4. For effective wind areas between those given, value may be interpolated, otherwise use the value associated with the lower effective wind area. 

5. Notation: 

a =* 10% of least horizontal dimension or 0. 4Ji, whichever is smaller, but not less than either 4% of least horizontal dimension or 0.9 m. 

h = mean roof height, m, except that the eave height shall be used for 6 < 10° 

0 — angle of plane of roof from horizontal, ° 


Figure 207E.5-1 

Design Wind Pressures Walls and Roofs, h < 18 m 
Enclosed Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


Wall Roof > 27 to 45 degrees Roof >7 to 27 degrees Roof 0 to 7 degrees 


2-170 CHAPTER 2 - Minimum Design Loads 


4 


Net Design Wind Pressure, p net (kPa) (Exposure B at h, = 10 m with / — 1.0 and K d — 1.0) 




-1 

.50 

-1 

.38 

-1 

.10 



Note: For effective areas between those given above the load may be interpolated, otherwise use the load associated with the lower effective 


area . The final value, including all permitted reductions, used in the design shall not be less than that required by Section 207E.2.2. 


Figure 207E.5-1 (continued) 

Design Wind Pressures on Walls and Roofs of Enclosed Buildings with h < 18 m 

Components and Cladding 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 

























































































































CHAPTER 2 - Minimum Design Loads 


2-171 


Roof Overhang Net Design Wind Pressure, p net (kPa) 
(Exposure B at h = 10 m with / = 1.0 and K d = 1.0) 



Zone 

Effective 

wind 

area 

(sq.m) 

Basic Wind Speed V (kph) 

150 

200 

250 

300 

350 

<U 

01 

0 i 

2 

0.9 

- 1.19 

- 2.12 

- 3.31 

- 4.76 

- 6.48 

2 

1.9 

- 1.17 

- 2.08 

- 3.25 

- 4.69 

- 10.27 

2 

4.6 

- 1.14 

- 2.03 

- 3.17 

- 4.57 

- 6.38 

'O 

h- 

2 

9.3 

- 1.13 

- 2.00 

- 3.13 

- 4.51 

- 8.21 

o 

-'M 

3 

0.9 

- 1.89 

- 3.35 

- 5.24 

- 7.55 

- 6.22 

o 

3 

1.9 

- 1.51 

- 2.68 

- 4,19 

- 6.03 

- 5.45 

© 

3 

4.6 

- 1.00 

- 1.78 

- 2.78 

- 4.00 

- 6.14 


3 

9.3 

- 1.25 

- 2.23 

- 3.48 

- 5.02 

- 6.83 

<U 

2 

0.9 

- 1.51 

- 2.68 

- 4.19 

- 6.03 

- 8.21 

u 

0JD 

2 

1.9 

- 1.51 

- 2.68 

- 4.19 

- 6.03 

- 13.38 

V 

'U 

2 

4.6 

- 1.51 

- 2.68 

- 4.19 

- 6.03 

- 8.21 

r- 

2 

9.3 

- 1.51 

- 2.68 

- 4.19 

- 6.03 

- 12.17 

o 

3 

0.9 

- 2.46 

- 4.37 

- 6.82 

- 9.83 

- 8.21 

h- 

A 

3 

1.9 

- 2.24 

- 3.97 

- 6.21 

- 8.94 

- 10.45 

c 

3 

4.6 

- 1.92 

- 3.41 

- 5.33 

- 7.67 

- 8.21 

S 

3 

9.3 

- 1.70 

- 3.02 

- 4.71 

- 6.79 

- 9.24 

cn 

<U 

2 

0.9 

- 1.38 

- 2.45 

- 3.83 

- 5.52 

- 7.52 

!U 

b£ 

2 

1.9 

- 1.35 

- 2.40 

- 3.75 

- 5.40 

- 7.52 

'O 

2 

4.6 

- 1.29 

- 2.29 

- 3.57 

- 5.14 

- 7.34 


2 

9.3 

- 1.25 

- 2.23 

- 3.48 

- 5.02 

- 7.34 

s 

l> 

3 

0.9 

- 1.38 

- 2.45 

- 3.83 

- 5.52 

- 7.00 

<N 

A 

3 

1.9 

- 1.35 

- 2.40 

- 3.75 

- 5.40 

- 7.00 

«4— 1 

o 

3 

4.6 

- 1.29 

- 2.29 

- 3.57 

- 5.14 

- 6.83 

o 

od 

3 

9.3 

- 1.25 

- 2.23 

- 3.48 

- 5.02 

- 6.83 


Adjustment Factor 
for Building Height and Exposure, A 


Mean roof height 
(m) 

Exposure 

B 

C 

D 

4.5 

1.00 

1.21 

1.47 

6.0 

1.00 

1.29 

1.55 

7.5 

1.00 

1.35 

1.61 

9.0 

1.00 

1.40 

1.66 

10.5 

1.05 

1.45 

1.70 

12.0 

1.09 

1.49 

1.74 

13.5 

1.12 

1.53 

1.78 

15.0 

1.16 

1.56 

1.81 

16.5 

1.19 

1.59 

1.84 

18.0 

1.22 

1.62 

1.87 


Figure 207E.5-1 (continued) 

Design Wind Pressures on Walls and Roofs of Enclosed Buildings with h < 18 m 

Components and Cladding 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-172 


CHAPTER 2 - Minimum Design Loads 





WALL ELEVATION 


Notes: 


1 . 

2 . 

3 . 

4. 

5. 

6 . 

7. 

8 . 


Vertical scale denotes GC„ to he used with appropriate q, or q h . 

Missis's - t ^ respectiveiy - 

Use rt with positive values of CC„ and q h with negative values of GC„. 

ssr iif.3 - «, — *-*- « - c - — * 

ffTXm” ^id«l around the P .,l-,«r of ft. roof with » < 10" , Zo.e ) shah he «.,.d a, Z.ue 2. 

Notation: 


a 

h 


z 

6 


1 0% of least horizontal dimension, but not less than 0.9 m. 

mean rooflwighl, Jtt, except that cave height shall be used for 6 _ 1 • 

he i glu above ground, ni 

angle of plane of roof from horizontal, ° 

Figure 207E.6-1 

External Pressure Coefficients, GC p Walls and Roofs, h > 18 m 
Enclosed, Partially Enclosed Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


r 


CHAPTER 2 - Minimum Design Loads 2-1 


Windward parapet Leeward parapet 

Load Case A Load Case B 


Top parapet 




Windward Parapet 

Load Case A 

L Windward parapet pressure (p t ) is determined using the positive wall pressure (p 5 ) zones 4 or 5 from Table 207E.7-2. 
2. Leeward parapet pressure (p 2 ) is determined using the negative roof pressure (p 7 ) zones 2 or 3 from Table 207E.7-2. 

Leeward Parapet 

Load Case B 

1 . Windward parapet pressure (p 3 ) is determined using the positive wall pressure (p 5 ) zones 4 or 5 from Table 207E.7-2. 

2. Leeward parapet pressure (p 4 ) is determined using the negative wall pressure (p 6 ) zones 4 or 5 from Table 207E.7-2. 

Figure 207E.7-1 

Parapet Wind Loads Application of Parapet Wind Loads, h < 48.8 m 
Enclosed Simple Diaphragm Buildings 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-174 CHAPTER 2 - Minimum Design Loads 



Vovh ~ 1-0 x roof pressure p from tables for edge Zones 1, 2 

Povh ~ 1 . 1 5 x roof pressure p from tables for comer Zone 3 


Notes: 

1 • Povh ~ roof pressure at overhang for edge or comer zone as applicable from figures in roof pressure table. 

2. Povh fr° m figures includes load from both top and bottom surface of overhang. 

3. Pressure p s at soffit of overhang can be assumed same as wall pressure, p w . 

Figure 207E.7-2 

Roof Overhang Wind Loads Application of Overhang Wind Loads, h < 48 
Enclosed Simple Diaphragm Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design I oads 


2-175 



/ 


Roof 

Angle 

e 

Effective 
Wind Area 


Clear Wind Flow 

Obstructed Wind Flow 

Zone 3 

Zone 2 

Zone 1 

Zone 3 

Zone 2 

Zone 1 

0° 

< 3 2 

2.4 

-3.3 

1.8 

-1.7 

1.2 

-1.1 

1 

-3.6 

0.8 

-1.8 

0.5 

-1.2 

> a 2 , 

< 4.0a 2 

1.8 

-1.7 

1.8 

-1.7 

1.2 

-1.1 

0.8 

-1.8 

0.8 

-1.8 

0.5 

-1.2 

> 4.0a 2 

1.2 

-1.1 

1.2 

-1.1 

1.2 

-1.1 

0.5 

-1.2 

0.5 

-1.2 

0.5 

-1.2 

7.5° 

< a 2 

3.2 

-4.2 

2.4 

-2.1 

1.6 

-1.4 

1.6 

-5.1 

1.2 

-2.6 

0.8 

-1.7 

> a 2 , 

< 4.0a 2 

2.4 

-2.1 

2.4 

-2.1 

1.6 

-1.4 

1.2 

-2.6 

1.2 

-2.6 

0.8 

-1.7 

> 4.0a 2 

1.6 

-1.4 

1.6 

-1.4 

1.6 

-1.4 

0.8 

-1.7 

0.8 

-1.7 

0.8 

-1.7 

15° 

< a 2 

3.6 

-3.8 

2.7 

-2.9 

1.8 

-1.9 

2.4 

-4.2 

1.8 

-3.2 

1.2 

-2.1 

> a 2 , 

< 4.0a 2 

2.7 

-2.9 

2.7 

-2.9 

1.8 

-1.9 

1.8 

-3.2 

1.8 

-3.2 

1.2 

-2.1 

> 4.0a 2 

1.8 

-1.9 

1.8 

-1.9 

1.8 

-1.9 

1.2 

-2.1 

1.2 

-2.1 

1.2 

-2.1 

30° 

< a 2 

5.2 

-5 

3.9 

-3.8 

2.6 

2.5 

3.2 

-4.6 

2.4 

-3.5 

1.6 

-2.3 

> a 2 , 

< 4.0a 2 

3.9 

-3.8 

3.9 

-3.8 

2.6 

2.5 

2.4 

-3.5 

2.4 

-3.5 

1.6 

-2.3 

> 4.0a 2 

2.6 

-2.5 

2.6 

-2.5 

2.6 

2.5 

1.6' 

-2.3 

1.6 

-2.3 

1.6 

-2.3 

45° 

< a 2 

5.2 

-4.6 

3.9 

-3.5 

2.6 

2.3 

4.2 

-3.8 

3.2 

-2.9 

2.1 

-1.9 

> a 2 , 

< 4.0a 2 

3.9 

-3.5 

3.9 

-3.5 

2.6 

2.3 

3.2 

-2.9 

3.2 

-2.9 

2.1 

-1.9 

> 4.0a 2 

2.6 

-2.3 

2.6 

-2.3 

2.6 

2.3 

2.1 

-1.9 

2.1 

-1.9 

2.1 

-1.9 


Notes: 



1. C N denotes net pressures (contributions from top and bottom surfaces). 

2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or equal to 50%. Obstructed wind flow denotes objects below roof 
inhibiting wind flow (>50% blockage). 

3. For values of 6 other than those shown, linear interpolation is permitted. 

4. Plus and minus signs signify pressures acting towards and away from the top roof surface, respectively. 

5. Components and cladding elements shall be designed for positive and negative pressure coefficients shown. 

6. Notation: 

a = 10% of least horizontal dimension or 0.4/i, whichever is smaller but not less than 4% of least horizontal dimension or 0.9 m. 

h ' m mean roof height, m 

L — Horizontal dimension of building, measured in along wind direction, m 

8 ~ angle of plane of roof from horizontal, ° 


Figure 207E.8-1 

Net Pressure Coefficient, C N Monoslope Free Roofs, 6 < 45°, 0.25< h/L < 1.0 

Open Buildings 


National Structural Code of the Philippines Volume l p 7th Edition, 2015 


2-176 CHAPTER 2 - Minimum Design Loads 




777777777777777777777 



Roof 

Effective 

4 - ~~1 

Angle 

Wind Area 

Clear Wind Flow 

Obstructed Wind Flow 

0 


Zone 3 

Zone 2 

Zone 1 

Zone 3 

Zor 

ie 2 

Zor 

ie 1 


< a 2 

2.4 

- 3.3 

1.8 

- 1.7 

1.2 

- 1.1 

i 

- 3.6 

0.8 

- 1.8 

0.5 

- 1.2 

0 ° 

> a 2 , 

< 4 . 0a 2 

1.8 

- 1.7 

1.8 

- 1.7 

1.2 

- 1.1 

0.8 

- 1.8 

0.8 

- 1.8 

0.5 

- 1.2 


> 4 . 0a 2 

1.2 

- 1.1 

1.2 

- 1.1 

1.2 

- 1.1 

0.5 

- 1.2 

0.5 

- 1.2 

0.5 

- 1.2 


< a 2 

2.2 

- 3.6 

1.7 

- 1.8 

1.1 

- 1.2 

1 

- 5.1 

0.8 

- 2.6 

0.5 

- 1.7 

7.5° 

> a 2 , 

< 4 . 0a 2 

1.7 

- 1.8 

1.7 

- 1.8 

1.1 

- 1.2 

0.8 

- 2.6 

0.8 

- 2.6 

0.5 

- 1.7 


> 4 . 0a 2 

i.i 

- 1.2 

1.2 

- 1.2 

1.1 

- 1.2 

0.5 

- 1.7 

0.5 

- 1.7 

0.5 

- 1.7 


< a 2 

2.2 

- 2.2 

1.7 

- 1.7 

i.i 

- 1.1 

1 

- 3.2 : 

0.8 

- 2.4 

0.5 

- 1.6 

15° 

> a 2 , 

< 4 . 0a 2 

1.7 

- 1.7 

1.7 

- 1.7 

i.i 

- 1.1 

0.8 

- 2.4 

0.8 

- 2.4 

0.5 

- 1.6 


> 4 . 0a 2 

1.1 

- 1.1 

1.1 

- 1.1 

1.1 

- 1.1 

0.5 

- 1.6 

0.5 

- 1.6 

0.5 

- 1.6 


< a 2 

2.6 

- 1.8 

2 

- 1.4 

1.3 

- 0.9 

1 

- 2.4 

0.8 

- 1.8 

0.5 

- 1.2 

30° 

> a 2 , 

< 4 . 0a 2 

2 

- 1.4 

2 

- 1.4 

1.3 

- 0.9 

0.8 

- 1.8 

0.8 

- 1,8 

0.5 

- 1.2 


> 4 . 0a 2 

1.3 

- 0.9 

1.3 

- 0.9 

1.3 

- 0.9 

0.5 

- 1.2 

0.5 

- 1.2 

0.5 

- 1.2 


< a 2 

2.2 

- 1.6 

1.7 

- 1.2 

1.1 

- 0.8 

1 

- 2.4 

0.8 

- 1.8 

0.5 

- 1.2 

45° 

> a 2 , 

< 4 . 0a 2 

1.7 

- 1.2 

1.7 

- 1.2 

1.1 

- 0.8 

oo 

o 

- 1.8 

0.8 

- 1.8 

0.5 

- 1.2 


> 4 . 0a 2 

1.1 

- 0.8 

1.1 

- 0.8 

1.1 

- 0.8 

0.5 

- 1.2 

0.5 

- 1.2 

0.5 

- 1.2 


Notes: 

1 . C N denotes net pressures (contributions from top and bottom surfaces). 

2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or equal to 50%. Obstructed wind flow denotes objects below roof 
inhibiting wind flow (>50% blockage). 

3. For values of 0 other than those shown, linear interpolation is permitted. 

4. Plus and minus signs signify pressures acting towards and away from the top roof surface, respectively. 

5. Components and cladding elements shall be designed for positive and negative pressure coefficients shown. 

6. Notation: 

a = 1 0% of least horizontal dimension or 0. 4 h, whichever is smaller but not less than 4% of least horizontal dimension or 0.9 m. Dimension 

“a” is as shown in Figure 207E.8-1. 
h = mean roof height, m 

L Horizontal dimension of building, measured in along wind direction, m 

0 = angle of plane of roof from horizontal, ° 

Figure 207E . 8-2 

Net Pressure Coefficient , C N Pitched Free Roofs , 6 < 45 °, 0 . 25 < h/L < 1.0 

Open Buildings 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




CHAPTER 2 - Minimum Design Loads 2-177 


0 > 10 ° 




Roof 

Angle 

0 

Effective 
Wind Area 

Cn 

Clear Wind Flow 

Obstructed Wind Flow 

Zone 3 

Zone 2 

Zone 1 

Zone 3 

Zone 2 

Zone 1 

0° 

< a 2 

2.4 

- 3.3 

1.8 

- 1.7 

1.2 

- 1.1 

1 

- 3.6 

0.8 

- 1.8 

0.5 

- 1.2 

> a 2 , 

< 4.0a 2 

1.8 

- 1.7 

1.8 

- 1.7 

1.2 

- 1.1 

0.8 

- 1.8 

0.8 

- 1.8 

0.5 

- 1.2 

> 4.0a 2 

1.2 

- 1.1 

1.2 

- 1.1 

1.2 

- 1.1 

0.5 

- 1.2 

0.5 

- 1.2 

0.5 

- 1.2 

7 . 5 ° 

< a 2 

2.4 

- 3.3 

1.8 

- 1.7 

1.2 

- 1.1 

1 

- 4.8 

0.8 

- 2.4 

0.5 

- 1.6 

> a 2 , 

< 4.0a 2 

1.8 

- 1.1 

1.8 

- 1.7 

1.2 

- 1.1 

0.8 

- 2.4 

0.8 

- 2.4 

0.5 

- 1.6 

> 4.0a 2 

1.2 

- 1.1 

1.2 

- 1.1 

1.2 

- l.i 

0.5 

- 1.6 

0.5 

- 1.6 

0.5 

- 1.6 

15° 

< a 2 

2.2 

- 2.2 

1.7 

- 1.7 

1.1 

- 1.1 

1 

- 2.4 

0.8 

- 1.8 

0.5 

- 1.2 

> a 2 , 

< 4.0a 2 

1.7 

- 1.7 

1.7 

- 1.7 

1.1 

- l.i 

0.8 

- 1.8 

0.8 

- 1.8 

0.5 

- 1.2 

> 4.0a 2 

1.1 

- 1.1 

1.1 

- 1.1 

1.1 

- l.i 

0.5 

- 1.2 

0.5 

- 1.2 

0.5 

- 1.2 

30° 

< a 2 

1.8 

- 2.6 

1.4 

-2 

0.9 

- 1.3 

1 

- 2.8 

0.8 

- 2.1 

0.5 

- 1.4 

> a 2 , 

< 4.0a 2 

1.4 

-2 

1.4 

-2 

0.9 

- 1.3 

0 . 8 . 

- 2.1 

0.8 

- 2.1 

0.5 

- 1.4 

> 4.0a 2 

0.9 

- 1.3 

0.9 

- 1.3 

0.9 

- 1.3 

0.5 

- 1.4 

0.5 

- 1.4 

0.5 

- 1.4 

45° 

< a 2 

1.6 

- 2.2 

1.2 

- 1.7 

0.8 

- 1.1 

1 

- 2.4 

0.8 

- 1.8 

0.5 

- 1.2 

> a 2 , 

< 4.0a 2 

1.2 

- 1.7 

1.2 

- 1.7 

0.8 

- 1.1 

0.8 

- 1.8 

0.8 

- 1.8 

0.5 

- 1.2 

> 4.0a 2 

0.8 

- 1.1 

0.8 

- 1.1 

0.8 

- 1.1 

0.5 

- 1.2 

0.5 

- 1.2 

0.5 

- 1.2 


Notes: 

1 . C N denotes net pressures (contributions from top and bottom surfaces). 

2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or equal to 50%. Obstructed wind flow denotes objects below roof 
inhibiting wind flow (>50% blockage). 

3. For values of 9 other than those shown, linear interpolation is permitted. 

4. Plus and minus signs signify pressures acting towards and away from the top roof surface, respectively. 

5. Components and cladding elements shall be designed for positive and negative pressure coefficients shown. 

6. Notation: 

a — 10% of least horizontal dimension or 0.4h, whichever is smaller but not less than 4% of least horizontal dimension or 0,9 m. 

Dimension “a” is as shown in Figure 207E.8-1. 
h ~ mean roof height, m 

L — Horizontal dimension of building, measured in along wind direction, m 
9 ~ angle of plane of roof from horizontal, ° 

Figure 207E.8-3 

Net Pressure Coefficient, C N Troughed Free Roofs, 0 < 45°, 0.25< h/L < 1.0 

Open Buildings 

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2-178 


CHAPTER 2 - Minimum Design Loads 


Windward parapet 
Load Case A 


Leeward parapet 

Load Case B Top parapet 



Load Case A 


1 . Windward parapet pressure ( p 1 ) is determined using the positive wall pressure (p 5 ) zones 4 or 5 from the applicable figure. 

2. Leeward parapet pressure (p 2 ) is determined using the negative roof pressure (p 7 ) zones 2 or 3 from the applicable figure. 


Leeward Parapet 

Load Case B 

1 . Windward parapet pressure (p 3 ) is determined using the positive wall pressure (p 5 ) zones 4 or 5 from the applicable figure. 

2. Leeward parapet pressure (p 4 ) is determined using the negative wall pressure (p 6 ) zones 4 or 5 from the applicable figure. 


User Note: 

See Note 5 in Figure 207 E. 4-2 A and Note 
7 in Figure 207E.6-1 for reductions in 
component and cladding roof pressures 
when parapets 0.9 m or higher are 
present. 


Figure 207E.9-1 

Parapet Wind Loads C&C - Part 6, All Building Heights All Building Types 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 


2-179 



Notes: 

1 . Net roof pressure p orft on roof overhangs is determined from interior, edge or comer zones as applicable from figures. 

2. Net pressure p ovh from figures includes pressure contribution from top and bottom surfaces of roof overhang. 

3. Positive pressure at roof overhang soffit p s is the same as adjacent wall pressure p w . 

Figure 207E.10-1 

Wind Loading - Roof Overhangs, C&C, All Building Heights All Building Types 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-180 CHAPTER 2- Minimum Design Loads 


207F Wind Tunnel Procedure 

Wind tunnel testing is specified when a structure contains 
any of the characteristics defined in Sections 207B.1.3, 
207C.1.3, 207D.1.3, or 207E.1.3 or when the designer 
wishes to more accurately determine the wind loads. For 
some building shapes wind tunnel testing can reduce the 
conservatism due to enveloping of wind loads inherent in 
the Directional Procedure , Envelope Procedure , or 
Analytical Procedure for Components and Cladding. Also , 
wind tunnel testing accounts for shielding or channeling 
and can more accurately determine wind loads for a 
complex building shape than the Directional Procedure, 
Envelope Procedure, or Analytical Procedure for 
Components and Cladding. It is the intent of the code that 
any building or other structure be allowed to use the wind 
tunnel testing method to determine wind loads. 
Requirements for proper testing are given in Section 
207F.2. 

It is common practice to resort to wind tunnel tests when 
design data are required for the following wind- induced 
loads: 

1. Curtain wall pressures resulting from irregular 
geometry. 

2. Across-wind and/or torsional loads. 

3. Periodic loads caused by vortex shedding. 

4. Loads resulting from instabilities, such as flutter or 
galloping. 

Boundary-layer wind tunnels capable of developing flows 
that meet the conditions stipulated in Section 207 F. 2 
typically have test-section dimensions in the following 
ranges: width of 2 to 4 m, height of 2 to 3 m, and length of 
15 to 30 m. Maximum wind speeds are ordinarily in the 
range of 10 to 45 m/s. The wind tunnel may be either an 
open-circuit or closed circuit type. 

Three basic types of wind-tunnel test models are commonly 
used. These are designated as follows: (1) rigid Pressure 
Model (PM), (2) rigid high-frequency base balance model 
(H-FBBM), and (3) Aero-elastic Model (AM). One or more 
of the models may be employed to obtain design loads for 
a particular building or structure. The PM provides local 
peak pressures for design of elements, such as cladding 
and mean pressures, for the determination of overall mean 
loads. The H-FBBM measures overall fluctuating loads 
(aerodynamic admittance) for the determination of 
dynamic responses. When motion of a building or structure 
influences the wind loading, the AM is employed for direct 
measurement of overall loads, deflections, and 


accelerations. Each of these models, together with a model 
of the surroundings (proximity model), can provide 
information other than wind loads, such as snow loads on 
complex roofs, wind data to evaluate environmental impact 
on pedestrians, and concentrations of air-pollutant 
emissions for environmental impact determinations. 
Several references provide detailed information and 
guidance for the determination of wind loads and other 
types of design data by wind tunnel tests (Cermak 1977, 
Reinhold 1982, ASCE 1999, and Boggs andPeterka 1989). 

Wind tunnel tests frequently measure wind loads that are 
significantly lower than required by Sections 207 A, 207 B, 
207 C, 207 D, and 207 E due to the shape of the building, the 
likelihood that the highest wind speeds occur at directions 
where the building ’s shape or pressure coefficients are less 
than their maximum values, specific buildings included in 
a detailed proximity model that may provide shielding in 
excess of that implied by exposure categories, and 
necessaiy conservatism in enveloping load coefficients in 
Sections 207C and 207E. In some cases, adjacent 
structures may shield the structure sufficiently that 
removal of one or two structures could significantly 
increase wind loads. Additional wind tunnel testing without 
specific nearby buildings (or with additional buildings if 
they might cause increased loads through channeling or 
buffeting) is an effective method for determining the 
influence of adjacent buildings. 

For this reason, the code limits the reduction that can be 
accepted from wind tunnel tests to 80 percent of the result 
obtained from Part 1 of Section 207B or Part 1 of Section 
207C, or Section 207E, if the wind tunnel proximity model 
included any specific influential buildings or other objects 
that, in the judgment of an experienced wind engineer, are 
likely to have substantially influenced the results beyond 
those characteristic of the general surroundings. If there 
are any such buildings or objects, supplemental testing can 
be performed to quantify their effect on the original results 
and possibly justify a limit lower than 80 percent, by 
removing them from the detailed proximity model and 
replacing them with characteristic ground roughness 
consistent with the adjacent roughness. A specific 
influential building or object is one within the detailed 
proximity model that protrudes well above its 
surroundings, or is unusually close to the subject building, 
or may otherwise cause substantial sheltering effect or 
magnification of the wind loads. When these supplemental 
test results are included with the original results, the 
acceptable results are then considered to be the higher of 
both conditions. 

However, the absolute minimum reduction permitted is 65 
percent of the baseline result for components and cladding, 
and 50 percent for the main wind force resisting system. A 
higher reduction is permitted for MWFRS, because 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 


J-1.fi 1 


components and cladding loads are more subject to 
changes due to local channeling effects when surroundings 
change and can easily be dramatically increased when a 
new adjacent building is constructed. It is also recognized 
that cladding failures are much more common than failures 
of the MWFRS . In addition , for the case of MWFRS it is 
easily demonstrated that the overall drag coefficient for 
certain common building shapes, such as circular 
cylinders especially with rounded or domed tops, is one- 
half or less of the drag coefficient for the rectangular 
prisms that form the basis of Section 207B, 207 C, and 
207 E. 

For components and cladding, the 80-percent limit is 
defined by the interior zones 1 and 4 in Figures 207E.4-1, 
207E.4-2A, 207 E. 4-2 B, 207E.4-2C, 207E.4-3, 207E.4-4, 
207 E. 4-5 A, 207E.4-5B, 207E.4-6, 207E.4-7, and 207 E. 5- 

1. This limitation recognizes that pressures in the edge 
zones are the ones most likely to be reduced by the specific 
geometry* of real buildings compared to the rectangular 
prismatic buildings assumed in Section 207 E. Therefore, 
pressures in edge and corner zones are permitted to be as 
low as 80 percent of the interior pressures from Section 
207E without the supplemental tests . The 80 percent limit 
based on zone 1 is directly applicable to all roof areas, and 
the 80 percent limit based on zone 4 is directly applicable 
to all wall areas. 

The limitation on MWFRS loads is more complex because 
the load effects (e.g., member stresses or forces, 
deflections) at any point are the combined effect of a vector 
of applied loads instead of a simple scalar value. In general 
the ratio of forces or moments or torques (force 
eccentricity) at various floors throughout the building 
using a wind tunnel study will not be the same as those 
ratios determined from Sections 207 B and 207C, and 
therefore comparison between the two methods is not well 
defined. Requiring each load effect from a wind tunnel test 
to be no less than 80 percent of the same effect resulting 
from Sections 207B and 207 C is impractical and 
unnecessarily complex and detailed, given the approximate 
nature of the 80 percent value. Instead, the intent of the 
limitation is effectively implemented by applying it only to 
a simple index that characterizes the overall loading. For 
flexible (tall) buildings, the most descriptive index of 
overall loading is the base overturning moment. For other 
buildings, the overturning moment can be a poor 
characterization of the overall loading, and the base shear 
is recommended instead '. 


207F.1 Scope 

The Wind Tunnel Procedure shall be used where required 
by Sections 207B.1.3, 207C.1.3, and 207D. 1.3. The Wind 
Tunnel Procedure shall be permitted for any building or 
structure in lieu of the design procedures specified in 
Section 207B (MWFRS for buildings of all heights and 
simple diaphragm buildings with h < 49 m, Section 207C 
(MWFRS of low-rise buildings and simple diaphragm low- 
rise buildings), Section 207D (MWFRS for all other 
structures), and Section 207E (components and cladding 
for all building types and other structures). 


User Note; 

Section 207F may always be used for determining wind 
pressures for the MWFRS and/or for C&C of any 
building or structure. This method is considered to 
produce the most accurate wind pressures of any 
method specified in this Code. 


207F.2 Test Conditions 

Wind tunnel tests, or similar tests employing fluids other 
than air, used for the determination of design wind loads 
for any building or other structure, shall be conducted in 
accordance with this section. Tests for the determination of 
mean and fluctuating forces and pressures shall meet all of 
the following conditions: 

1. The natural atmospheric boundary layer has been 
modeled to account for the variation of wind speed 
with height. 

2. The relevant macro-(integral) length and micro-length 
scales of the longitudinal component of atmospheric 
turbulence are modeled to approximately the same 
scale as that used to model the building or structure. 

3. The modeled building or other structure and 
surrounding structures and topography are 
geometrically similar to their full-scale counterparts, 
except that, for low-rise buildings meeting the 
requirements of Section 207C.1.2, tests shall be 
permitted for the modeled building in a single 
exposure site as defined in Section 207 A. 7. 3. 

4. The projected area of the modeled building or other 
structure and surroundings is less than 8 percent of the 
test section cross-sectional area unless correction is 
made for blockage. 

5. The longitudinal pressure gradient in the wind tunnel 
test section is accounted for. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-182 CHAPTER 2 - Minimum Design Loads 


6. Reynolds number effects on pressures and forces are 
minimized. 

7. Response characteristics of the wind tunnel 
instrumentation are consistent with the required 
measurements. 

207F.3 Dynamic Response 

Tests for the purpose of determining the dynamic response 
of a building or other structure shall be in accordance with 
Section 207F.2. The structural model and associated 
analysis shall account for mass distribution, stiffness, and 
damping. 

207F.4 Load Effects 

207F.4.1 Mean Recurrence Intervals of Load Effects 

The load effect required for Strength Design shall be 
determined for the same mean recurrence interval as for the 
Analytical Method, by using a rational analysis method, 
defined in the recognized literature, for combining the 
directional wind tunnel data with the directional 
meteorological data or probabilistic models based thereon. 
The load effect required for Allowable Stress Design shall 
be equal to the load effect required for Strength Design 
divided by 1.6. For buildings that are sensitive to possible 
variations in the values of the dynamic parameters, 
sensitivity studies shall be required to provide a rational 
basis for design recommendations. 

Commentary: 

Examples of analysis methods for combining directional 
wind tunnel data with the directional meteorological data 
or probabilistic models based thereon are described in 
Lepage and Irwin (1985), Rigato etal. (2001), Isyumov et 
al. (2003), Irwin et al (2005), Simiu and Filliben (2005), 
and Simiu and Miyata (2006). 

207F.4.2 Limitations on Wind Speeds 

The wind speeds and probabilistic estimates based thereon 
shall be subject to the limitations described in Section 
207A.5.3. 

Commentary: 

Section 207F.4.2 specifies that the statistical methods used 
to analyze historical wind speed and direction data for 
wind tunnel studies shall be subject to the same limitations 
specified in Section 207 F. 4. 2 that apply to the Analytical 
Method. 


Database-Assisted Design. Wind-tunnel aerodynamics 
databases that contain records of pressures measured 
synchronously at large numbers of locations on the 
exterior surface of building models have been developed by 
wind researchers, e.g., Simiu et al. (2003) and Main and 
Fritz (2006). Such databases include data that permit a 
designer to determine, without specific wind tunnel tests, 
wind-induced forces and moments in Main Wind Force 
Resisting Systems and Components and Cladding of 
selected shapes and sizes of buildings. A public domain set 
of such databases, recorded in tests conducted at the 
University of Western Ontario (Ho et al. 2005 and St. 
Pierre et al. 2005) for buildings with gable roofs is 
available on the National Institute of Standards and 
Technology (NIST) website: www.nist.gov/wind. 
Interpolation software for buildings with similar shape and 
with dimensions close to and intermediate between those 
included in the set of databases is also available on that 
site. Because the database results are for generic 
surroundings as permitted in item 3 of Section 207 F. 2 , 
interpolation or extrapolation from these databases should 
be used only if condition 2 of Section 207B.1.2 is true. 
Extrapolations from available building shapes and sizes 
are not permitted, and interpolations in some instances 
may not be advisable. For these reasons, the guidance of 
an engineer experienced in wind loads on buildings and 
familiar with the usage of these databases is recommended. 
All databases must have been obtained using testing 
methodology that meets the requirements for wind tunnel 
testing specified in Section 207F. 

207F.4.3 Limitations on Loads 

Loads for the main wind force resisting system determined 
by wind tunnel testing shall be limited such that the overall 
principal loads in the x and y directions are not less than 80 
percent of those that would be obtained from Part 1 of 
Section 207B or Part 1 of Section 207C. The overall 
principal load shall be based on the overturning moment 
for flexible buildings and the base shear for other buildings. 

Pressures for components and cladding determined by 
wind tunnel testing shall be limited to not less than 80 
percent of those calculated for Zone 4 for walls and Zone 
1 for roofs using the procedure of Section 207E. These 
Zones refer to those shown in Figures 207E.4-1, 207E.4- 
2A, 207E.4-2B, 207E.4-2C, 207E.4-3, 207E.4-4, 207E.4- 
5 A, 207E.4-5B, 207E.4-6, 207E.4-7, and 207E.6-1. 

The limiting values of 80 percent may be reduced to 50 
percent for the main wind force resisting system and 65 
percent for components and cladding if either of the 
following conditions applies: 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 


2-183 


1. There were no specific influential buildings or objects 
within the detailed proximity model. 

2. Loads and pressures from supplemental tests for all 
significant wind directions in which specific 
influential buildings or objects are replaced by the 
roughness representative of the adjacent roughness 
condition, but not rougher than exposure B, are 
included in the test results. 

207F.5 Wind-Borne Debris 

Glazing in buildings in wind-borne debris regions shall be 

protected in accordance with Section 207A.10.3. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2- 184 CHAPTER 2 Minimum Design Loads 


SECTION 208 
EARTHQUAKE LOADS 

208.1 General 

208.1.1 Purpose 

The purpose of the succeeding earthquake provisions is 
primarily to design seismic-resistant structures to 
safeguard against major structural damage that may lead to 
loss of life and property. These provisions are not intended 
to assure zero-damage to structures nor maintain their 
functionality after a severe earthquake. 

208.1.2 Minimum Seismic Design 

Structures and portions thereof shall, as a minimum, be 
designed and constructed to resist the effects of seismic 
ground motions as provided in this section. 

208.1.3 Seismic and Wind Design 

When the code-prescribed wind design produces greater 
effects, the wind design shall govern, but detailing 
requirements and limitations prescribed in this section and 
referenced sections shall be made to govern. 

208.2 Definitions 

See Section 202. 

208.3 Symbols and Notations 

A b = ground floor area of structure to include area 
covered by all overhangs and projections, m 2 
A c = the combined effective area of the shear walls in 
the first storey of the structure, m 2 
A e = the minimum cross-sectional area in any 
horizontal plane in the first storey of a shear wall, 
m 2 

A x = the torsional amplification factor at Level x 
a p = numerical coefficient specified in Section 208.7 
and set forth in Table 208-13 
C a = seismic coefficient, as set forth in Table 208-7 
C t = numerical coefficient given in Section 208.5.2.2 
C v = seismic coefficient, as set forth in Table 208-8 
D = dead load 

D e = the length of a shear wall in the first storey in the 
direction parallel to the applied forces, m 
E,E h ,E m ,E v = earthquake loads set forth in Section 
208.6 

F x = design seismic force applied to Level i, n or x , 
respectively 

F p = design seismic force on a part of the structure 
F px = design seismic force on a diaphragm 


F t = that portion of the base shear, V, considered 
concentrated at the top of the structure in addition 
to F n 

lateral force at Level i for use in Equation 208- 

/i “ 14 

g = acceleration due to gravity = 9.815 m/sec 2 

h if h n , h x = height above the base to Level i, n or x , 
respectively, m 

/ = importance factor given in Table 208-1 

I p = importance factor for nonstructural component as 
given in Table 208-1 
L = live load 

Level i = level of the structure referred to by the 
subscript i 

“i = 1” designates the first level above the base 
Level n = that level that is uppermost in the main 
portion of the structure 

Level x = that level that is under design consideration 
“x = 1” designates the first level above the base 
M = maximum moment magnitude 
N a = near-source factor used in the determination of C a 
in Seismic Zone 4 related to both the proximity of 
the building or structure to known faults with 
magnitudes as set forth in Tables 208-4 and 208-5 
N v = near-source factor used in the determination of C v 
in Seismic Zone 4 related to both the proximity of 
the building or structure to known faults with 
magnitudes as set forth in Tables 208-4 and 208-6 
PI = plasticity index of soil determined in accordance 
with approved national standards 
R = numerical coefficient representative of the inherent 
over-strength and global ductility capacity of 
lateral-force-resisting systems, as set forth in Table 
208-11 or 208-12 

r = a ratio used in determining pDDthe 
redundancy/reliability factor. See Section 208.5. 
Sa>Sb’S c ,S d ,S e ,S f = soil profile types as set forth 

in Table 208-2 

T = elastic fundamental period of vibration of the 
structure in the direction under consideration, 
sec 

V = base shear given by Equations. 208-8, 208-9, 
208-10, 208-11 or 208-15 
V x - the design storey shear in Storey x 

W — the total seismic dead load defined in Section 

208.5.2.1 

w l> w x = that portion of W located at or assigned to 
Level i or x, respectively 
W v ~ the weight of an element or component 
w px = the weight of the diaphragm and the element 
tributary thereto at Level x , including applicable 
portions of other loads defined in Section 

208.6.1 

Z — seismic zone factor as given in Table 208-3 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 Minimum Design Loads 2 185 


A M Maximum Inelastic Response Displacement, 

which is the total drift or total storey drift that 
occurs when the structure is subjected to the 
Design Basis Ground Motion, including 
estimated elastic and inelastic contributions to 
the total deformation defined in Section 
208.6.4.2, mm 

A s Design Level Response Displacement, which is 

the total drift or total storey drift that occurs 
when the structure is subjected to the design 
seismic forces, mm 

Si horizontal displacement at Level i relative to the 

base due to applied lateral forces, f h for use in 
Equation 208-14, mm 

p Redundancy/Reliability Factor given by 

Equation 208-20 

ft 0 Seismic Force Amplification Factor, which is 

required to account for structural over-strength 
and set forth in Table 208-1 1 

208.4 Basis for Design 

208.4.1 General 

The procedures and the limitations for the design of 
structures shall be determined considering seismic zoning, 
site characteristics, occupancy, configuration, structural 
system and height in accordance with this section. 
Structures shall be designed with adequate strength to 
withstand the lateral displacements induced by the Design 
Basis Ground Motion, considering the inelastic response of 
the structure and the inherent redundancy, over-strength 
and ductility of the lateral force-resisting system. 

The minimum design strength shall be based on the Design 
Seismic Forces determined in accordance with the static 
lateral force procedure of Section 208.5, except as 
modified by Section 208.5.3.5.4. 

Where strength design is used, the load combinations of 
Section 203.3 shall apply. Where Allowable Stress Design 
is used, the load combinations of Section 203.4 shall apply. 

Allowable Stress Design may be used to evaluate sliding 
or overturning at the soil-structure interface regardless of 
the design approach used in the design of the structure, 
provided load combinations of Section 203.4 are utilized. 


208.4.2 Occupancy Categories 

For purposes of earthquake-resistant design, each structure 
shall be placed in one of the occupancy categories listed in 
Table 103-1. Table 208-1 assigns importance factors, / and 
/ p , and structural observation requirements for each 
category. 


Table 208-1 - Seismic Importance Factors 


Occupancy 
Category 1 

Seismic 
Importance 
Factor, I 

Seismic 
Importance 2 
Factor, I p 

I. Essential 
Facilities 3 

1.50 

1.50 

II. Hazardous 
Facilities 

1.25 

1.50 

III. Special 

Occupancy 

Structures 

1.00 

1.00 

IV, Standard 
Occupancy 
Structures 

1.00 

1.00 

V. Miscellaneous 
structures 

1.00 

1.00 


1 See Table 103-1 for occupancy category listing 

2 The limitation of I p for panel connections in Section 
208. 7.2.3 shall be 1.0 for the entire connector 

3 Structural observation requirements are given in Section 
107.9 

4 For anchorage of machinery and equipment required for 
life-safety systems, the value of I p shall be taken as 1.5 

208.4.3 Site Geology and Soil Characteristics 

Each site shall be assigned a soil profile type based on 
properly substantiated geotechnical data using the site 
categorization procedure set forth in Section 208.4.3.1.1 
and Table 208-2. 

Exception: 

When the soil properties are not known in sufficient detail 
to determine the soil profile type, Type S D shall be used. 
Soil Profile Type S E or S F need not be assumed unless the 
building official determines that Type S E or S F may be 
present at the site or in the event that Type S E or S F is 
established by geotechnical data. 


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2-186 CHAPTER 2 - Minimum Design Loads 


208.4.3.1 Soil Profile Type 

Soil Profile Types S A , S B , S c , S D and are defined in 

Table 208-2 and Soil Profile Type S F is defined as soils 

requiring site-specific evaluation as follows: 

1. Soils vulnerable to potential failure or collapse under 
seismic loading, such as liquefiable soils, quick and 
highly sensitive clays, and collapsible weakly 
cemented soils. 

2. Peats and/or highly organic clays, where the thickness 
of peat or highly organic clay exceeds 3.0 m. 

3 . Very high plasticity clays with a plasticity index, PI > 
75, where the depth of clay exceeds 7.5 m. 


5. The criteria set forth in the definition for Soil Profile 
Type S F requiring site-specific evaluation shall be 
considered. If the site corresponds to these criteria, the 
site shall be classified as Soil Profile Type S F and a 
site-specific evaluation shall be conducted. 

208.4.3.1.1 Site Categorization Procedure 

208.4.3.1.1.1 Scope 

This section describes the procedure for determining Soil 

Profile Types S A through S F as defined in Table 208-2. 


4. 


Very thick soft/medium stiff clays, where the depth of 
clay exceeds 35 m. 

Table 208-2 - Soil Profile Types 


Soil Profile 
Type 

Soil Profile Name / Generic 
Description 

Average Soil Properties for Top 30 m of Soil Profile 

Shear Wave Velocity, 

V s (m/s) 

SPT, N( blows/ 
300 mm) 

Undrained 

Shear 

Strength, S v 
(kPa) 

Sa 

Hard Rock 

> 1500 



S b 

Rock 

760 to 1500 

Sr 

Very Dense Soil and Soft Rock 

360 to 760 

>50 

> 100 


Stiff Soil Profile 

180 to 360 

15 to 50 

50 to 100 

Sb 1 

Soft Soil Profile 

< 180 

< 15 

<50 

S F 

Soil Requiring Site-specific Evaluation. 

See Section 208.4.3.1 


1 Soil Profile Type S E also includes any soil profile with more than 3.0 m of soft clay defined as a soil with plasticity index , 
PI > 20 , w mc > 40% and s u < 24 kPa. The Plasticity Index , PI, and the moisture content , w mc , shall be determined 
in accordance with approved national standards. 


208.4.3.1.1.2 Definitions 

Soil profile types are defined as follows: 

S A Hard rock with measured shear wave velocity, 

v s > 1500 m/s 

S B Rock with 760 m/s < v s < 1500 m/s 

S c Very dense soil and soft rock with 360 m/s < 

v s < 760 m/s or with either N > 50 or s u > 

100 kPa 

S D Stiff soil with 180 m/s <vs< 360 m/s or 

with 15 < IV < 50 or 50 kPa < s u < 

100 kPa 


S E A soil profile with v s < 180 m/s or any 
profile with more than 3 m of soft clay defined 
as soil with PI > 20, w mc > 40 percent and 

s u < 25 kPa 

S F Soils requiring site-specific evaluation, refer to 
Section 208.4.3.1 


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208.4.3.1.1.2.1 v s , Average Shear Wave Velocity 

v s shall be determined in accordance with the following 
equation: 


s v „ dj_ (208-1) 

Li= 1 v sl 

where 

di = thickness of Layer i , m 

v si = shear wave velocity in Layer i , m/s 

208.4.3.1.1.2.2 Af, Average Field 
Standard Penetration Resistance and 
N ch , Average Standard Penetration 
Resistance for Cohesionless Soil 
Layers 

N and N cfl shall be determined in accordance with the 
following equation: 

N =^i± 

" yn di (208-2) 

^i=i N . 


Nch (208-3) 

U=t N. 

where 

d t = thickness of Layer i in mm 

d s = the total thickness of cohesionless soil layers 
in the top 30 m 

N t = the standard penetration resistance of soil 
layer in accordance with approved nationally 
recognized standards 

208.4.3.1.1.2.3 s u , Average Undrained Shear 
Strength 

s u shall be determined in accordance with the following 
equation: 


208.4.3.1.1.2.4 Rock Profiles, S A and S B 

The shear wave velocity for rock, Soil Profile Type S B , 
shall be either measured on site or estimated by a 
geotechnical engineer, engineering geologist or 
seismologist for competent rock with moderate fracturing 
and weathering. Softer and more highly fractured and 
weathered rock shall either be measured on site for shear 
wave velocity or classified as Soil Profile Type S c . 

The hard rock, Soil Profile Type S A , category shall be 
supported by shear wave velocity measurement either on 
site or on profiles of the same rock type in the same 
formation with an equal or greater degree of weathering 
and fracturing. Where hard rock conditions are known to 
be continuous to a depth of 30 m, surficial shear wave 
velocity measurements may be extrapolated to assess v s . 
The rock categories, Soil Profile Types S A and S B , shall 
not be used if there is more than 3 meters of soil between 
the rock surface and the bottom of the spread footing or mat 
foundation. 

The definitions presented herein shall apply to the upper 
30 m of the site profile. Profiles containing distinctly 
different soil layers shall be subdivided into those layers 
designated by a number from 1 to n at the bottom, where 
there are a total of n distinct layers in the upper 30 m. The 
symbol i then refer to any one of the layers between 1 and 
n. 

208.4.3.1.1.2.5 Soft Clay Profile, S E 

The existence of a total thickness of soft clay greater than 
3 m shall be investigated where a soft clay layer is defined 
by s u < 24 kPa, w mc > 40 percent and PI > 20. If 
these criteria are met, the site shall be classified as Soil 
Profile Type S E . 

208.4.3.1.1.2.6 Soil Profiles S c , S D and S E 

Sites with Soil Profile Types S c , S D and S E shall be 
classified by using one of the following three methods with 
v s , N and s u computed in all cases as specified in Section 
208.4.3.1.1.2. 


where 



“ v „ A (2°8- 4 ) 

the total thickness (100 — d s ) of cohesive 
soil layers in the top 30 m 
the undrained shear strength in accordance 
with approved nationally recognized 
standards, not to exceed 250 kPa 

National Structural Code of the Philippii 


1. v s for the top 30 meters (v s method). 

2. N for the top 30 meters (N method). 

3. N ch for cohesionless soil layers {PI < 20) in the top 
30 m and average s u for cohesive soil layers {PI > 
20) in the top 30 m (s u method). 

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2-188 CHAPTER 2 - Minimum Design Loads 


208.4.4 Site Seismic Hazard Characteristics 

Seismic hazard characteristics for the site shall be 
established based on the seismic zone and proximity of the 
site to active seismic sources, site soil profile 
characteristics and the structure's importance factor. 

208.4.4.1 Seismic Zone 

The Philippine archipelago is divided into two seismic 
zones only. Zone 2 covers the provinces of Palawan 
(except Busuanga) , Sulu and Tawi-Tawi while the rest of 
the country is under Zone 4 as shown in Figure 208-1. Each 
structure shall be assigned a seismic zone factor Z, in 
accordance with Table 208-3. 


Table 208-3 Seismic Zone Factor Z 


ZONE 

2 

4 

Z 

0.20 

0.40 


208.4.4.2 Seismic Source Types 

Table 208-4 defines the types of seismic sources. The 
location and type of seismic sources to be used for design 
shall be established based on approved geological data; see 
Figure 208-2A. Type A sources shall be determined from 
Figure 208-2B, 2C, 2D, 2E or the most recent mapping of 
active faults by the Philippine Institute of Volcanology and 
Seismology (PHIVOLCS). 


Table 208-4 - Seismic Source Types 1 


Seismic 

Source 

Type 

Seismic Source 
Description 

Seismic Source 
Definition 

Maximum Moment 
Magnitude, M 

A 

Faults that are 
capable of 
producing large 
magnitude events 
and that have a 
high rate of seismic 
activity. 

7.0 < M < 8.4 

B 

All faults other 
than Types A and 

C. 

6.5 < M < 7.0 

C 

Faults that are not 
capable of 
producing large 
magnitude 
earthquakes and 
that have a 
relatively low rate 
of seismic activity. 

M < 6.5 


*S ubduction sources shall be evaluated on a site- 
specific basis. 


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CHAPTER 2 - Minimum Design Loads 



Figure 208-1 Referenced Seismic Map of the Philippines 
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2-190 CHAPTER 2 - Minimum Design Loads 



Distribution of Active Faults and Trenches 
in the Philippines 


Figure 208-2A Distribution of Active Faults and Trenches in the Philippines 
Association of Structural Engineers of the Philippines, Inc, (ASEP) 



CHAP! ER 2 — Minimum Design Loads 


2401 



Distribution of Active Faults in 
Cordillera Administrative Region (CAR) 


Earthquake Sourest 
Active Faults 
— — JUMMw.eaottttwWn 

Dashed hoe - trace is approximate 
Approxrmala oflahore projection 

• Capital City /Municipality 


0 IQ 20 JO 40 SO 


\ 


Figure 208-2B Distribution of Active Faults in Cordillera Administrative Region (CAR) 
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2-192 CHAPTER 2 - Minimum Design Loads 



Distribution of Active Faults and Trenches 

in Region 1 


Earthquake Sources 
Active Faults 

tx*l f kp« rn (■!*■» 

OMhad IM - boo* I* ^nninM 

Converg en ce Zone 

****** TfwnJi 


Figure 208-2C Distribution of Active Faults and Trenches in Region 1 
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CHAPTER 2 - Minimum Design Loads 2-193 



Distribution of Active Faults and Trenches 

in Region 2 


Figure 208-2D Distribution of Active Faults and Trenches in Region 2 
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Association of Structural Engineers of the Philippines, Inc. (ASEP) 


Distribution of Active Faults 
Region 3 





Figure 208-2F Distribution of Active Faults and Trenches in Region 4A 

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2-196 CHAPTER 2 - Minimum Design Loads 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 


Distribution of Active Faults and Trenches 
in Region 4B 




Figure 208-2E Distribution of Active Faults in Region 5 
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Distribution of Active Faults and Trenches in Region 6 



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2-199 


Distribution of Active Faults in Region 7 



Figure 208-2G Distribution of Active Faults in Region 7 


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;\ 

m. 


NORTHERN SAMAR 


Distribution of Active Faults in Region 8 


Earthquake Sources 
Active Faults 

Betid £r* ■ V9i*> it MfUWf 
- - - Dashed lira - (race Is approximate 
Approximate offshore projection 


Capital City /Municipality 


Figure 208-2H Distribution of Active Faults in Region 8 


Association of Structural Engineers of the Philippines, Inc, (ASEP) 




Distribution of Active Faults and Trenches in 
Autonomous Region of Muslim Mindanao (ARMM) 


CHAPTER 2 - Minimum Design Loads 2-201 



Figure 208-21 Distribution of Active Faults and Trenches in Autonomous Region of Muslim Mindanao (ARMM) 


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2*202 CHAPTER Z— Minimum Design Loads 


Distribution of Active Faults and Trenches in Region 9 



Figure 208-2J Distribution of Active Faults and Trenches in Region 9 


Association of Structural Engineers of the Philippines. Inc. (ASEP) 





Figure 208-2K Distribution of Active Faults and Trenches in Region 10 


, 


2-203 


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Distribution of Active Faults and Trenches 

in Region 11 



Figure 208-2L Distribution of Active Faults in Region 1 1 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




C H A P T E R 2 - Minii li u m D m i g « L o ads 


2-205 



Distribution of Active Faults and Trenches 


Figure 208-2M Distribution of Active Faults and Trenches in Region 12 
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Distribution of Active Faults and Trenches 

in Region 13 



Figure 208-2N Distribution of Active Faults and Trenches in Region 13 


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CHAPTER 2 - Minimum Design Loads 2-207 


208.4.4.3 Seismic Zone 4 Near-Source Factor 

Jn Seismic Zone 4, each site shall be assigned near-source 
factors in accordance with Tables 208-5 and 208-6 based 
on the Seismic Source Type as set forth in Section 
208.4.4.2. 


4. The exceptions to Section 515.6.5 shall not apply, 
except for columns in one-storey buildings or columns 
at the top storey of multistorey buildings. 

5. None of the following structural irregularities is 
present: Type 1, 4 or 5 of Table 208-9, and Type l or 
4 of Table 208-10. 


For high rise structures and essential facilities within 
2.0 km of a major fault, a site specific seismic elastic design 
response spectrum is recommended to be obtained for the 
specific area. 


Table 208-5 Near-Source Factor N a 1 


Seismic 

Closest Distance To 

Source 

Known Seismic Source 2 

T y.P e 

<2 km 

< 5 km 

> 10 km 

A 

1.5 

1.2 

1.0 

B 

1.3 

1.0 

1.0 

C 

1.0 

1.0 

1.0 


Table 208-6 Near-Source Factor, N v 1 


Seismic 

Source 

Type 

Closest Distance To 

Known Seismic Source 2 

<2 km 

5 km 

10 km 

> 15 km 

A 

2.0 

1.6 

1.2 

1.0 

B 

1.6 

1.2 

1.0 

1.0 

C 

1.0 

1.0 

1.0 

1.0 


Notes for Tables 208.5 and 208.6: 

1 The Near-Source Factor may be based on the linear 
interpolation of values for distances other than those 
shown in the table. 

2 The closest distance to seismic source shall be taken 
as the minimum distance between the site and the area 
described by the vertical projection of the source on 
the surface (i.e., surface projection of fault plane). The 
surface projection need not include portions of the 
source at depths of 10 km or greater. The largest value 
of the Near-Source Factor considering all sources 
shall be used for design. 

The value of N a used to determine C a need not exceed 1 . 1 

for structures complying with all the following conditions: 


208.4.4,4 Seismic Response Coefficients 

Each structure shall be assigned a seismic coefficient, C a , 
in accordance with Table 208-7 and a seismic coefficient, 
C v , in accordance with Table 208-8. 


Table 208-7 Seismic Coefficient, C a 


Soil Profile 
Type 

Seismic Zone Z 

Z = 0.2 

Z = 0.4 

S A 

0.16 

0.32 N a 

Sm 

0.20 

0A0N n 

Sr 

0.24 

0A0N a 

S D 

0.28 

0A4N a 

Sf 

0.34 

0A4N a 

Sf 

See Footnote 1 of Table 208-8 


Table 208-8 Seismic Coefficient, C v 


Soil Profile 
Type 

Seismic Zone Z 

Z = 0.2 

Z = 0.4 

S A 

0.16 

0.32AV 

Sn 

0.20 

OAONv 

Sr 

0.32 

0.56AV 

Sn 

0.40 

0.64AT 

Sjj 

0.64 

0.96AV 

s, 

See Footnote 1 of Table 208-8 


! Site-specific geotechnical investigation and dynamic site 
response analysis shall be performed to determine 
seismic coefficients 


208.4.5 Configuration Requirements 

Each structure shall be designated as being structurally 
regular or irregular in accordance with Sections 208.4.5.1 
and 208.4.5.2. 


1 . The soil profile type is S A , S B , S c or S D . 

2 . p= 1 . 0 . 

3. Except in single-storey structures, residential building 
accommodating 10 or fewer persons, private garages, 
carports, sheds and agricultural buildings, moment 
frame systems designated as part of the lateral-force- 
resisting system shall be special moment-resisting 
frames. 


208.4.5.1 Regular Structures 

Regular structures have no significant physical 
discontinuities in plan or vertical configuration or in their 
lateral-force-resisting systems such as the irregular features 
described in Section 208.4.5.2. 


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2-208 CHAPTER 2 - Minimum Design Loads 


208.4.5.2 Irregular Structures 

1. Irregular structures have significant physical 
discontinuities in configuration or in their lateral- 
force-resisting systems. Irregular features include, but 
are not limited to, those described in Tables 208-9 and 
208-10. All structures in occupancy Categories 4 and 
5 in Seismic Zone 2 need to be evaluated only for 
vertical irregularities of Type 5 (Table 208-9) and 
horizontal irregularities of Type 1 (Table 208-10). 

2. Structures having any of the features listed in Table 
208-9 shall be designated as if having a vertical 
irregularity. 

Exception: 

Where no storey drift ratio under design lateral forces is 
greater them 1.3 times the storey drift ratio of the storey 
above, the structure may be deemed to not have the 
structural irregularities of Type / or 2 in Table 208-9. The 
store}’ drift ratio for the top two stories need not he 
considered. The storey drifts for this determination may be 
calculated neglecting torsional effects. 

3. Structures having any of the features listed in Table 
208-10 shall be designated as having a plan 
irregularity. 


Table 208-9 Vertical Structural Irregularities 


Irregularity Type and Definition 

Reference 

Section 

1. Stiffness Irregularity - Soft 
Storey 

A soft storey is one in which the 
lateral stiffness is less than 70 % of 
that in the storey above or less than 
80 percent of the average stiffness 
of the three stories above. 

208.4.8.3 

Item 2 

2. Weight (Mass) Irregularity 

Mass irregularity shall be 

considered to exist where the 
effective mass of any storey is more 
than 150 % of the effective mass of 
an adjacent storey. A roof that is 
lighter than the floor below need 
not be considered. 

208.4.8.3 

Item 2 

3. Vertical Geometric Irregularity 

Vertical geometric irregularity shall 
be considered to exist where the 
horizontal dimension of the lateral- 
force-resisting system in any storey 
is more than 130 % of that in an 
adjacent storey. One-storey 

penthouses need not be considered. 

208.4.8.3 
Item 2 

4. In-Plane Discontinuity In 

Vertical Lateral-Force-Resisting 
Element Irregularity 

An in-plane offset of the lateral- 
load-resisting elements greater than 
the length of those elements. 

208.5.8.1.5. 

1 

5. Discontinuity In Capacity - 
Weak Storey Irregularity 

A weak storey is one in which the 
storey strength is less than 80 % of 
that in the storey above. The storey 
strength is the total strength of all 
seismic-resisting elements sharing 
the storey for the direction under 
consideration. 

208.4.9.1 


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CHAPTER 2 - Minimum Design Loads 2-209 


Table 208-10 Horizontal Structural Irregularities 


Irregularity Type and Definition 

Reference 

Section 

1. Torsional Irregularity - To Be 

Considered When Diaphragms Are 
Not Flexible 

Torsional irregularity shall be 
considered to exist when the 
maximum storey drift, computed 
including accidental torsion, at one 
end of the structure transverse to an 
axis is more than 1.2 times the 
average of the storey drifts of the two 
ends of the structure. 

208.7.2.7 
Item 6 

2. Re-Entrant Corner Irregularity 

Plan configurations of a structure and 
its lateral-force-resisting system 
contain re-entrant corners, where both 
projections of the structure beyond a 
re-entrant corner are greater than 1 5 
% of the plan dimension of the 
structure in the given direction. 

208.7.2.7 
Items 6 
and 7 

3. Diaphragm Discontinuity 
Irregularity 

Diaphragms with abrupt 

discontinuities or variations in 
stiffness, including those having 
cutout or open areas greater than 50 % 
of the gross enclosed area of the 
diaphragm, or changes in effective 
diaphragm stiffness of more than 50 
% from one storey to the next. 

208.7.2.7 
Item 6 

4. Out-Of-Plane Offsets Irregularity 

Discontinuities in a lateral force path, 
such as out-of-plane offsets of the 
vertical elements 

208.5.8.5. 

1 

208.7.2.7 
Item 6; 

5. Non-parallel Systems Irregularity 

The vertical lateral-load-resisting 
elements are not parallel to or 
symmetric about the major orthogonal 
axes of the lateral force-resisting 
systems. 

208.7.1 


208.4.6 Structural Systems 

Structural systems shall be classified as one of the types 
listed in Table 208-1 1 and defined in this section. 

208.4.6.1 Bearing Wall System 

A structural system without a complete vertical load- 
carrying space frame. Bearing walls or bracing systems 
provide support for all or most gravity loads. Resistance to 
lateral load is provided by shear walls or braced frames. 

208.4.6.2 Building Frame System 

A structural system with an essentially complete space 
frame providing support for gravity loads. Resistance to 
lateral load is provided by shear walls or braced frames. 

208.4.6.3 Moment-Resisting Frame System 

A structural system with an essentially complete space 
frame providing support for gravity loads. Moment- 
resisting frames provide resistance to lateral load primarily 
by flexural action of members. 

208.4.6.4 Dual System 

A structural system with the following features: 

1. An essentially complete space frame that provides 
support for gravity loads. 

2. Resistance to lateral load is provided by shear walls or 
braced frames and moment-resisting frames (SMRF, 
IMRF, MMRWF or steel OMRF). The moment- 
resisting frames shall be designed to independently 
resist at least 25 percent of the design base shear. 

3. The two systems shall be designed to resist the total 
design base shear in proportion to their relative 
rigidities considering the interaction of the dual system 
at all levels. 


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208.4.6.5 Cantilevered Column System 

A structural system relying on cantilevered column 
elements for lateral resistance. 

208.4.6.6 Undefined Structural System 
A structural system not listed in Table 208-1 1 . 

208.4.6.7 Non-building Structural System 
A structural system conforming to Section 208.8. 

208.4.7 Height Limits 

Height limits for the various structural systems in Seismic 
Zone 4 are given in Table 208-1 1 . 

Exception: 

Regular structures may exceed these limits by not more 
than 50 percent for unoccupied structures, which are not 
accessible to the general public. 


208.4.8 Selection of Lateral Force Procedure 

Any structure may be, and certain structures defined below 
shall be, designed using the dynamic lateral-force 
procedures of Section 208.5.3. 

208.4.8.1 Simplified Static 

The simplified static lateral-force procedure set forth in 
Section 208.5. 1 . 1 may be used for the following structures 
of Occupancy Category IV or V: 

1 . Buildings of any occupancy (including single-family 
dwellings) not more than three stories in height 
excluding basements that use light-frame construction. 

2. Other buildings not more than two stories in height 
excluding basements. 

208.4.8.2 Static 

The static lateral force procedure of Section 208.5 may be 
used for the following structures: 

1. All structures, regular or irregular in Occupancy 
Categories IV and V in Seismic Zone 2. 

2. Regular structures under 75 m in height with lateral 
force resistance provided by systems listed in Table 
208-11, except where Section 208.4.8.3, Item 4, 
applies. 

3. Irregular structures npt more than five stories or 20 m 
in height. 

4. Structures having a llexible upper portion supported 
on a rigid lower portion where both portions of the 
structure considered separately can be classified as 
being regular, the average storey stiffness of the lower 
portion is at least 10 times the average storey stiffness 
of the upper portion and the period of the entire 
structure is not greater than 1.1 times the period of the 
upper portion considered as a separate structure fixed 
at the base. 


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CHAPTER 2 - Minimum Design Loads 2-21 1 


208.4.8.3 Dynamic 

The dynamic lateral-force procedure of Section 208.5.3 
shall be used for all other structures, including the 
following: 

1 . Structures 75 m or more in height, except as permitted 
by Section 208.4.8,2, Item 1. 

2. Structures having a stiffness, weight or geometric 
vertical irregularity of Type 1, 2 or 3, as defined in 
Table 208-9, or structures having irregular features not 
described in Table 208-9 or 208-10, except as 
permitted by Section 208.4.10.3.1. 

3. Structures over five stories or 20 m in height in 
Seismic Zone 4 not having the same structural system 
throughout their height except as permitted by Section 
208.5.3.2. 

4. Structures, regular or irregular, located on Soil Profile 
Type S f , that have a period greater than 0.7 s. The 
analysis shall include the effects of the soils at the site 
and shall conform to Section 208.5.3.2, Item 4. 

208.4.8.4 Alternative Procedures 

208.4.8.4.1 General 

Alternative lateral-force procedures using rational analyses 
based on well-established principles of mechanics may be 
used in lieu of those prescribed in these provisions. 

208.4.8.4.2 Seismic Isolation 

Seismic isolation, energy dissipation and damping systems 
may be used in the analysis and design of structures when 
approved by the building official and when special 
detailing is used to provide results equivalent to those 
obtained by the use of conventional structural systems. 


208.4.9 System Limitations 

208.4.9.1 Discontinuity 

Structures with a discontinuity in capacity, vertical 
irregularity Type 5 as defined in Table 208-9, shall not be 
over two stories or 9 m in height where the weak storey has 
a calculated strength of less than 65 % of the storey above. 

Exception : 

Where the weak storey is capable of resisting a total lateral 
seismic force of fl 0 times the design force prescribed in 
Section 208.5 . 

208.4.9.2 Undefined Structural Systems 

For undefined structural systems not listed in Table 208- 
11, the coefficient R shall be substantiated by approved 
cyclic test data and analyses. The following items shall be 
addressed when establishing R: 

1 . Dynamic response characteristics, 

2. Lateral force resistance, 

3. Over-strength and strain hardening or softening, 

4. Strength and stiffness degradation, 

5. Energy dissipation characteristics, 

6. System ductility, and 

7. Redundancy. 

208.4.9.3 Irregular Features 

All structures having irregular features described in Table 
208-9 or 208-10 shall be designed to meet the additional 
requirements of those sections referenced in the tables. 

208.4.10 Determination of Seismic Factors 

208.4.10.1 Determination offl 0 

For specific elements of the structure, as specifically 
identified in this code, the minimum design strength shall 
be the product of the seismic force over-strength factor H 0 
and the design seismic forces set forth in Section 208.5. For 
both Allowable Stress Design and Strength Design, the 
Seismic Force Over- strength Factor, shall be taken 
from Table 208-11. 


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208.4.10.2 Determination of R 

The value for R shall be taken from Table 208-1 1 . 

208.4.10.3 Combinations of Structural Systems 

Where combinations of structural systems are incorporated 
into the same structure, the requirements of this section 
shall be satisfied. 

208.4.10.3.1 Vertical Combinations 

The value of R used in the design of any storey shall be less 
than or equal to the value of R used in the given direction 
for the storey above. 

Exception: 

This requirement need not be applied to a storey where the 
deadweight above that storey is less than 10 percent of the 
total dead weight of the structure. 

Structures may be designed using the procedures of this 
section under the following conditions: 

The entire structure is designed using the lowest R of the 
lateral force-resisting systems used, or 

1. The following two-stage static analysis procedures 
may be used for structures conforming to Section 
208.4.8.2, Item 4. 

1 . 1 The flexible upper portion shall be designed as a 
separate structure, supported laterally by the rigid 
lower portion, using the appropriate values of R 
and p. 

1.2 The rigid lower portion shall be designed as a 
separate structure using the appropriate values of 
R and p. The reactions from the upper portion 
shall be those determined from the analysis of the 
upper portion amplified by the ratio of the ( R / p) 
of the upper portion over (R/p) of the lower 
portion. 

208.4.10.3.2 Combinations along Different Axes 

In Seismic Zone 4 where a structure has a bearing wall 
system in only one direction, the value of R used for design 
in the orthogonal direction shall not be greater than that 
used for the bearing wall system. 

Any combination of bearing wall systems, building frame 
systems, dual systems or moment-resisting frame systems 
may be used to resist seismic forces in structures less than 
50 m in height. Only combinations of dual systems and 
special moment-resisting frames shall be used to resist 


seismic forces in structures exceeding 50 m in height in 
Seismic Zone 4. 

208.4.10.3.3 Combinations along the Same Axis 

Where a combination of different structural systems is 
utilized to resist lateral forces in the same direction, the 
value of R used for design in that direction shall not be 
greater than the least value for any of the systems utilized 
in that same direction. 

208.5 Minimum Design Lateral Forces and Related 
Effects 

208.5.1 Simplified Static Force Procedure 

Structures conforming to the requirements of Section 

208.4.8.1 may be designed using this procedure. 

208.5.1.1 Simplified Design Base Shear 

The total design base shear in a given direction shall be 
determined from the following equation: 

V = —W (208-5) 

R 

where the value of C a shall be based on Table 208-7 for the 
soil profile type. When the soil properties are not known 
in sufficient detail to determine the soil profile type. Type 
S D shall be used in Seismic Zone 4, and Type S E shall be 
used in Seismic Zone 2. In Seismic Zone 4, the Near- 
Source Factor, N a , need not be greater than 1 .2 if none of 
the following structural irregularities are present: 

1 . Type 1 , 4 or 5 of Table 208-9, or 

2. Type 1 or 4 of Table 208-10. 

208.5.1.2 Vertical Distribution 

The forces at each level shall be calculated using the 
following equation: 

F=^ Wl (208-6) 


where the value of C a shall be determined as in Section 
208.5.1.1. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


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208.5.1.3 Horizontal Distribution of Shear 

The design storey shear, V x , in any storey is the sum of the 
forces F t and F x above that storey. V x shall be distributed 
to the various elements of the vertical lateral force-resisting 
system in proportion to their rigidities, considering the 
rigidity of the diaphragm. See Section 208.7.2.3 for rigid 
elements that are not intended to be part of the lateral force- 
resisting systems. 


where 

8 avg = ^e average of the displacements at the 
extreme points of the structure at Level x, 
mm 

8 max = the maximum displacement at Level x , 
mm 

The value of A x need not exceed 3.0 


Where diaphragms are not flexible, the mass at each level 
shall be assumed to be displaced from the calculated center 
of mass in each direction a distance equal to 5 percent of 
the building dimension at that level perpendicular to the 
direction of the force under consideration. The effect of 
this displacement on the storey shear distribution shall be 
considered. 

Diaphragms shall be considered flexible for the purposes 
of distribution of storey shear and torsional moment when 
the maximum lateral deformation of the diaphragm is more 
than two times the average storey drift of the associated 
storey. This may be determined by comparing the 
computed midpoint in-plane deflection of the diaphragm 
itself under lateral load with the storey drift of adjoining 
vertical-resisting elements under equivalent tributary 
lateral load. 


208.5.1.5 Overturning 

Every structure shall be designed to resist the overturning 
effects caused by earthquake forces specified in Section 
208,5.2,3. At any level, the overturning moments to be 
resisted shall be determined using those seismic forces ( F t 
and F x ) that act on levels above the level under 
consideration. At any level, the incremental changes of the 
design overturning moment shall be distributed to the 
various resisting elements in the manner prescribed in 
Section 208.5.1.3. Overturning effects on every element 
shall be carried down to the foundation. See Sections 207. 1 
and 208.7 for combining gravity and seismic forces. 

208.5.1.5.1 Elements Supporting Discontinuous 

Systems 

208.5.1.5.1.1 General 


208.5.1.4 Horizontal Torsional Moments 

Provisions shall be made for the increased shears resulting 
from horizontal torsion where diaphragms are not flexible. 
The most severe load combination for each element shall 
be considered for design. 

The torsional design moment at a given storey shall be the 
moment resulting from eccentricities between applied 
design lateral forces at levels above that storey and the 
vertical-resisting elements in that storey plus an accidental 
torsion. 

The accidental torsional moment shall be determined by 
assuming the mass is displaced as required by Section 
208.5.1.3. 


Where any portion of the lateral load-resisting system is 
discontinuous, such as for vertical irregularity Type 4 in 
Table 208-9 or plan irregularity Type 4 in Table 208-10, 
concrete, masonry, steel and wood elements supporting 
such discontinuous systems shall have the design strength 
to resist the combination loads resulting from the special 
seismic load combinations of Section 203.5. 

Exceptions: 

1. The quantity E m in Section 208.6 need not exceed the 
maximum force that can be transferred to the element 
by the lateral-force-resisting system. 

2. Concrete slabs supporting light-frame wood shear 
wall systems or light-frame steel and wood structural 
panel shear wall systems . 


Where torsional irregularity exists, as defined in Table 
208-10, the effects shall be accounted for by increasing the 
accidental torsion at each level by an amplification factor, 
A x , determined from the following equation: 




1 . 26 , 


avf]} 


(208-7) 


For Allowable Stress Design, the design strength may be 
determined using an allowable stress increase of 1 .7 and a 
resistance factor, 0, of 1.0. This increase shall not be 
combined with the one- third stress increase permitted by 
Section 203.4, but may be combined with the duration of 
load increase permitted in Section 615.3.4. 


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208.5.1.5.1-1-2 Detailing requirements in Seismic 
Zone 4 

In Seismic Zone 4, elements supporting discontinuous 

systems shall meet the following detailing or member 

limitations: 

1 . Reinforced concrete or reinforced masonry elements 
designed primarily as axial-load members shall 
comply with Section 421.4.4.5. 

2. Reinforced concrete elements designed primarily as 
flexural members and supporting other than light- 
frame wood shear wall system or light-frame steel and 
wood structural panel shear wall systems shall comply 
with Sections 421.3.2 and 421.3.3. Strength 
computations for portions of slabs designed as 
supporting elements shall include only those portions 
of the slab that comply with the requirements of these 
sections. 

3. Masonry elements designed primarily as axial-load 
carrying members shall comply with Sections 
706.1.12.4, Item 1, and 708.2.6.2.6. 

4. Masonry elements designed primarily as flexural 
members shall comply with Section 708.2.6.2.5. 

5. Steel elements designed primarily as axial-load 
members shall comply with Sections 515.4.2 and 
515.4.3. 

6. Steel elements designed primarily as flexural members 
or trusses shall have bracing for both top and bottom 
beam flanges or chords at the location of the support 
of the discontinuous system and shall comply with the 
requirements of Section 515.6.1.3. 

7. Wood elements designed primarily as flexural 
members shall be provided with lateral bracing or 
solid blocking at each end of the element and at the 
connection location(s) of the discontinuous system. 


208.5.1.6 Applicability 

Sections 208.6.2, 208.6.3, 208.5.2.1, 208.5.2.2, 208.5.2.3, 
208.6.4,208.6.5 and 208.5.3 shall not apply when using the 
simplified procedure. 

Exception: 

For buildings with relatively flexible structural systems, 
the building official may require consideration of PA 
effects and drift in accordance with Sections 208.63, 
208.6.4 and 208.6.5. A s shall be determined using design 
seismic forces from Section 208.5.1.1. 

Where used, A M shall be taken equal to 0.01 times the 
storey height of all stories. In Section 208.7.2.7, 

Equation 208-22 shall read F px = ~^w V x and need not 
exceed C a w px , but shall not be less than 0. 5 C a w px . R and 
fl 0 shall be taken from Table 208-11. 

208.5.2 Static Force Procedure 

208.5.2.1 Design Base Shear 

The total design base shear in a given direction shall be 
determined from the following equation: 

v = £lL W (208-8) 

RT 

The total design base shear need not exceed the following: 

2 / 

v= a W (208-9) 

R 

The total design base shear shall not be less than the 
following: 

F = 0 .11 C a IW (208-10) 


208.5.1.5.2 At Foundation 

See Sections 208.4.1 and 308.4 for overturning moments 
to be resisted at the foundation soil interface. 


In addition, for Seismic Zone 4, the total base shear shall 
also not be less than the following: 


0. 8 ZNJ 

V - —W 

R 


(208-11) 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-215 


208.5.2.2 Structure Period 

The value of T shall be determined from one of the 
following methods: 


distribution. The elastic deflections, S h shall be calculated 
using the applied lateral forces, /*. 

208.5.2.3 Vertical Distribution of Force 


1. Method A: 

For all buildings, the value T may be approximated from 
the following equation: 


The total force shall be distributed over the height of the 
structure in conformance with Equations 208-15, 208-16 
and 208-17 in the absence of a more rigorous procedure. 


T = C t (h n ) 3/ * (208-12) 


where 


V = F t +^F t 

i = 1 


(208-15) 


C t = 0.0853 for steel moment-resisting frames 

C t = 0.0731 for reinforced concrete moment- 

resisting frames and eccentrically braced 
frames 

C t = 0.0488 for all other buildings 


The concentrated force F t at the top, which is in addition 
to F n , shall be determined from the equation: 

F t = 0.077V (208-16) 


Alternatively, the value of C t for structures with concrete 
or masonry shear walls may be taken as 0.0743/V^: 

The value of A c shall be determined from the following 
equation: 


A c = ^A e [0.2 + (D e /h n ) 2 ] (208-13) 


The value of D e /h n used in Equation 208-13 shall not 
exceed 0.9. 

2. Method B: 

The fundamental period T may be calculated using the 
structural properties and deformational characteristics of 
the resisting elements in a properly substantiated analysis. 
The analysis shall be in accordance with the requirements 
of Section 208.6.2. The value of T from Method B shall 
not exceed a value 30 percent greater than the value of T 
obtained from Method A in Seismic Zone 4, and 40 percent 
in Seismic Zone 2. 


The value of T used for the purpose of calculating F t shall 
be the period that corresponds with the design base shear 
as computed using Equation 208-4. F t need not exceed 
0. 25F and may be considered as zero where T is 0.7 s or 
less. The remaining portion of the base shear shall be 
distributed over the height of the structure, including Level 
n, according to the following equation: 


(V~F t )w x h x 

w t h, 


(208-17) 


At each level designated as x , the force F x shall be applied 
over the area of the building in accordance with the mass 
distribution at that level. Structural displacements and 
design seismic forces shall be calculated as the effect of 
forces F x and F t applied at the appropriate levels above the 
base. 

208.5.3 Dynamic Analysis Procedures 
208.5.3.1 General 


The fundamental period T may be computed by using the 
following equation: 


T = 


. I (ZUwfi) 


(208-14) 


Dynamic analyses procedures, when used, shall conform to 
the criteria established in this section. The analysis shall be 
based on an appropriate ground motion representation and 
shall be performed using accepted principles of dynamics. 

Structures that are designed in accordance with this section 
shall comply with all other applicable requirements of 
these provisions. 


The values of f t represent any lateral force distributed 
approximately in accordance with the principles of 
Equations. 208-15, 208-16 and 208- 17 or any other rational 


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208.5.3.2 Ground Motion 

T£e ground motion representation shall, as a minimum, be 
one having a 10-percent probability of being exceeded in 
50 years, shall not be reduced by the quantity R and may 
be one of the following: 

h An elastic design response spectrum constructed in 
accordance with Figure 208-3, using the values of C a 
and C v consistent with the specific site. The design 
acceleration ordinates shall be multiplied by the 
acceleration of gravity, 9.815 m/sec 2 . 

2. A site-specific elastic design response spectrum based 
on the geologic, tectonic, seismologic and soil 
characteristics associated with the specific site. The 
spectrum shall be developed for a damping ratio of 
0.05, unless a different value is shown to be consistent 
with the anticipated structural behavior at the intensity 
of shaking established for the site. 

3. Ground motion time histories developed for the 
specific site shall be representative of actual 
earthquake motions. Response spectra from time 
histories, either individually or in combination, shall 
approximate the site design spectrum conforming to 
Section 208.5.3.2, Item 2, 


4. For structures on Soil Profile Type S F , the following 
requirements shall apply when required by Section 
208.4.8.3, Item 4: 

4. 1 The ground motion representation shall be 
developed in accordance with Items 2 and 3. 

4.2 Possible amplification of building response due to 
the effects of soil-structure interaction and 
lengthening of building period caused by inelastic 
behavior shall be considered. 

5. The vertical component of ground motion may be 
defined by scaling corresponding horizontal 
accelerations by a factor of two- thirds. Alternative 
factors may be used when substantiated by site- 
specific data. Where the Near-Source Factor, N a , is 
greater than 1 . 0 , site-specific vertical response spectra 
shall be used in lieu of the factor of two-thirds. 



Figure 208-3 
Design Response Spectra 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 Minimum Dfllign Loads 


2' 21 / 


208.5.3.3 Mathematical Model 

A mathematical model of the physical structure shall 
represent the spatial distribution of the mass and stiffness 
of the structure to an extent that is adequate for the 
calculation of the significant features of its dynamic 
response. A three-dimensional model shall be used for the 
dynamic analysis of structures with highly irregular plan 
configurations such as those having a plan irregularity 
defined in Table 208-10 and having a rigid or semi-rigid 
diaphragm. The stiffness properties used in the analysis 
and general mathematical modeling shall be in accordance 
with Section 208.6.2. 

208.5.3.4 Description of Analysis Procedures 

208.5.3.4.1 Response Spectrum Analysis 

An elastic dynamic analysis of a structure utilizing the peak 
dynamic response of all modes having a significant 
contribution to total structural response. Peak modal 

responses are calculated using the ordinates of the 
appropriate response spectrum curve which correspond to 
the modal periods. Maximum modal contributions are 
combined in a statistical manner to obtain an approximate 
total structural response. 

208.5.3.4.2 Time History Analysis 

An analysis of the dynamic response of a structure at each 
increment of time when the base is subjected to a specific 
ground motion time history. 

208.5.3.5 Response Spectrum Analysis 

208.5.3.5.1 Response Spectrum Representation 
and Interpretation of Results 

The ground motion representation shall be in accordance 
with Section 208.5.3.2. The corresponding response 
parameters, including forces, moments and displacements, 
shall be denoted as Elastic Response Parameters. Elastic 
Response Parameters may be reduced in accordance with 
Section 208.5.3.5.4. 

The base shear for a given direction, determined using 
dynamic analysis must not be less than the value obtained 
by the equivalent lateral force method of Section 208.5.2. 
In this case, all corresponding response parameters are 
adjusted proportionately. 

208.5.3.5.2 Number of Modes 

The requirement of Section 208.5.3.4.1 that all significant 
modes be included may be satisfied by demonstrating that 


for the modes considered, at least 90 percent of the 
participating mass of the structure is included in the 
calculation of response for each principal horizontal 
direction. 

208.5.3.5.3 Combining Modes 

The peak member forces, displacements, storey forces, 
storey shears and base reactions for each mode shall be 
combined by recognized methods. When three- 
dimensional models are used for analysis, modal 
interaction effects shall be considered when combining 
modal maxima. 

208.5.3.5.4 Reduction of Elastic Response 
Parameters for Design 

Elastic Response Parameters may be reduced for purposes 
of design in accordance with the following items, with the 
limitation that in no case shall the Elastic Response 
Parameters be reduced such that the corresponding design 
base shear is less than the Elastic Response Base Shear 
divided by the value of R. 

1 . For all regular structures where the ground motion 
representation complies with Section 208.5.3.2, Item 

1, Elastic Response Parameters may be reduced such 
that the corresponding design base shear is not less 
than 90 percent of the base shear determined in 
accordance with Section 208.5.2. 

2. For all regular structures where the ground motion 
representation complies with Section 208.5.3.2, Item 

2, Elastic Response Parameters may be reduced such 
that the corresponding design base shear is not less 
than 80 percent of the base shear determined in 
accordance with Section 208.5.2, 

3. For all irregular structures, regardless of the ground 
motion representation, Elastic Response Parameters 
may be reduced such that the corresponding design 
base shear is not less than 1 00 percent of the base shear 
determined in accordance with Section 208.5.2. 

The corresponding reduced design seismic forces shall be 
used for design in accordance with Section 203. 

208.5.3.5.5 Directional Effects 

Directional effects for horizontal ground motion shall 
conform to the requirements of Section 208.6. The effects 
of vertical ground motions on horizontal cantilevers and 
pre-stressed elements shall be considered in accordance 
with Section 208.6, Alternately, vertical seismic response 
may be determined by dynamic response methods; in no 


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2-218 CHAPTER 2 - Minimum Design Loads 


case shall the response used for design be less than that 
obtained by the static method. 

208.5.3.5.6 Torsion 

The analysis shall account for torsional effects, including 
accidental torsional effects as prescribed in Section 
208.5.1.4. Where three-dimensional models are used for 
analysis, effects of accidental torsion shall be accounted for 
by appropriate adjustments in the model such as adjustment 
of mass locations, or by equivalent static procedures such 
as provided in Section 208.5.1.3. 

208.5.3.5.7 Dual Systems 

Where the lateral forces are resisted by a dual system as 
defined in Section 208.4.6.4, the combined system shall be 
capable of resisting the base shear determined in 
accordance with this section. The moment-resisting frame 
shall conform to Section 208.4.6.4, Item 2, and may be 
analyzed using either the procedures of Section 208.5.2.3 
or those of Section 208.5.3.5. 

208.5.3.6 Time History Analysis 

208.5.3.6.1 Time History 

Time-history analysis shall be performed with pairs of 
appropriate horizontal ground-motion time- history 
components that shall be selected and scaled from not less 
than three recorded events. Appropriate time histories shall 
have magnitudes, fault distances and source mechanisms 
that are consistent with those that control the design-basis 
earthquake (or maximum capable earthquake). Where 
three appropriate recorded ground-motion time-history 
pairs are not available, appropriate simulated ground- 
motion time-history pairs may he used to make up the total 
number required. For each pair of horizontal ground- 
motion components, the square root of the sum of the 
squares (SRSS) of the 5 percent-damped site-specific 
spectrum of the scaled horizontal components shall be 
constructed. The motions shall be scaled such that the 
average value of the SRSS spectra does not fall below 1.4 
times the 5 percent-damped spectrum of the design-basis 
earthquake for periods from 0 . 2 T second to 1. 57 seconds. 
Each pair of time histories shall be applied simultaneously 
to the model considering torsional effects. 

The parameter of interest shall be calculated for each time- 
history analysis. If three time-history analyses are 
performed, then the maximum response of the parameter 
of interest shall be used for design. If seven or more time- 
history analyses are performed, then the average value of 
the response parameter of interest may be used for design. 


208.5.3.6.2 Elastic Time History Analysis 

Elastic time history shall conform to Sections 208.5.3.1, 
208.5.3.2, 208.5.3.3, 208.5.3.5.2, 208.5.3.5.4, 

208.6.5.3.5.5, 208.6.5.3.5.6, 208.5.3.5.7 and 208.5.3.6.1 
and 208.6.6.1. Response parameters from elastic time- 
history analysis shall be denoted as Elastic Response 
Parameters. All elements shall be designed using Strength 
Design. Elastic Response Parameters may be scaled in 
accordance with Section 208.5.3.5.4. 

208.5.3.6.3 Nonlinear Time History Analysis 

208.5.3.6.3.1 Nonlinear Time History 

Nonlinear time history analysis shall meet the requirements 
of Section 208.4.8.4, and time histories shall be developed 
and results determined in accordance with the requirements 
of Section 208.5.3.6.1. Capacities and characteristics of 
nonlinear elements shall be modeled consistent with test 
data or substantiated analysis, considering the Importance 
Factor. The maximum inelastic response displacement 
shall not be reduced and shall comply with Section 208.6.5. 

208.5.3.6.3.2 Design Review 

When nonlinear time-history analysis is used to justify a 
structural design, a design review of the lateral- force- 
res i sling system shall be performed by an independent 
engineering team, including persons licensed in the 
appropriate disciplines and experienced in seismic analysis 
methods. The lateral -force-resisting system design review 
shall include, but not be limited to, the following: 

1. Reviewing the development of site-specific spectra 
and ground-motion time histories. 

2. Reviewing the preliminary design of the lateral-force- 
resisting system. 

3. Reviewing the final design of the lateral-force- 
resisting system and all supporting analyses. 

The engineer-of-record shall submit with the plans and 
calculations a statement by all members of the engineering 
team doing the review stating that the above review has 
been performed. 


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CHART FR ? -- Minimum Design I oads 


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208.6 Earthquake Loads and Modeling 
Requirements 

208.6.1 Earthquake Loads 

Structures shall be designed for ground motion producing 
structural response and seismic forces in any horizontal 
direction. The following earthquake loads shall be used in 
the load combinations set forth in Section 203: 

E = pE h + E v (208-18) 

E m = n 0 E h (208-19) 

where 


r max ' s defined as the largest of the element storey shear 
ratios, r h which occurs in any of the storey levels at or 
below the two-thirds height level of the building. 

For braced frames, the value of r i is equal to the maximum 
horizontal force component in a single brace element 
divided by the total storey shear. 

For moment frames, r t shall be taken as the maximum of 
the sum of the shears in any two adjacent columns in a 
moment frame bay divided by the storey shear. For 
columns common to two bays with moment-resisting 
connections on opposite sides at Level i in the direction 
under consideration, 70 percent of the shear in that column 
may be used in the column shear summation. 


E 


E h 


Ev 


n n 


p 


the earthquake load on an element of the 
structure resulting from the combination of 
the horizontal component, E h , and the 
vertical component, E v 
the earthquake load due to the base shear, 
V, as set forth in Section 208.5.2 or the 
design lateral force, F p , as set forth in 
Section 208.9 

the estimated maximum earthquake force 
that can be developed in the structure as set 
forth in Section 208.6.1, and used in the 
design of specific elements of the structure, 
as specifically identified in this section 
the load effect resulting from the vertical 
component of the earthquake ground 
motion and is equal to an addition of 
0. 5 C a ID to the dead load effect, D, for 
Strength Design, and may be taken as zero 
for Allowable Stress Design 
the seismic force amplification factor that is 
required to account for structural 
overstrength, as set forth in Section 
208.4.10.1 

Reliability/Redundancy Factor as given by 
the following equation: 


P = 2~ 


6.1 



(208-20) 


where 

r max = the maximum element-storey shear ratio. 

For a given direction of loading, the 
element-storey shear ratio is the ratio of the 
design storey shear in the most heavily 
loaded single element divided by the total 
design storey shear. 


For shear walls, shall be taken as the maximum value of 
the product of the wall shear multiplied by 3 /l w and 
divided by the total storey shear, where l w is the length of 
the wall in meter. 

For dual systems, r i shall be taken as the maximum value 
of r t as defined above considering all lateral-load-resisting 
elements. The lateral loads shall be distributed to elements 
based on relative rigidities considering the interaction of 
the dual system. For dual systems, the value of p need not 
exceed 80 percent of the value calculated above. 

p shall not be taken less than 1.0 and need not be greater 
than 1.5. For special moment-resisting frames, except 
when used in dual systems, p shall not exceed 1.25. The 
number of bays of special moment-resisting frames shall 
be increased to reduce r, such that p is less than or equal 
to 1.25. 

Exception: 

Ab may be taken as the average floor area in the upper 
setback portion of the building where a larger base area 
exists at the ground floor. 

When calculating drift, or when the structure is located in 
Seismic Zone 2, p shall be taken equal to 1.0. 

The ground motion producing lateral response and design 
seismic forces may be assumed to act non-concurrently in 
the direction of each principal axis of the structure, except 
as required by Section 208.7.2. 

Seismic dead load, W , is the total dead load and applicable 
portions of other loads listed below. 

I , In storage and warehouse occupancies, a minimum of 
25 percent of the floor live load shall be applicable. 


For any given Storey Level i , the element- storey shear ratio 
is denoted as r*. The maximum element-storey shear ratio 

National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-220 CHAPTER 2 - Minimum Design Loads 


2. Where a partition load is used in the floor design, a 
load of not less than 0.5 kN/m 2 shall be included. 

3. Total weight of permanent equipment shall be 
included. 

208.6.2 Modeling Requirements 

The mathematical model of the physical structure shall 
include all elements of the lateral-force-resisting system. 
The model shall also include the stiffness and strength of 
elements, which are significant to the distribution of forces, 
and shall represent the spatial distribution of the mass and 
stiffness of the structure. In addition, the model shall 
comply with the following: 

1 . Stiffness properties of reinforced concrete and 
masonry elements shall consider the effects of cracked 
sections. 

2. For steel moment frame systems, the contribution of 
panel zone deformations to overall storey drift shall be 
included. 

208.6.3 PA Effects 

The resulting member forces and moments and the storey 
drifts induced by PA effects shall be considered in the 
evaluation of overall structural frame stability and shall be 
evaluated using the forces producing the displacements of 
A s . PA need not be considered when the ratio of secondary 
moment to primary moment does not exceed 0.10; the ratio 
may be evaluated for any storey as the product of the total 
dead and floor live loads, as required in Section 203, above 
the storey times the seismic drift in that storey divided by 
the product of the seismic shear in that storey times the 
height of that storey. In Seismic Zone 4, PA need not be 
considered when the storey drift ratio does not exceed 

0.02/P. 

208.6.4 Drift 

Drift or horizontal displacements of the structure shall be 
computed where required by this code. For both Allowable 
Stress Design and Strength Design, the Maximum Inelastic 
Response Displacement, A w , of the structure caused by the 
Design Basis Ground Motion shall be determined in 
accordance with this section. The drifts corresponding to 
the design seismic forces of Section 208.5.2.1 or Section 
208.5.3.5, A 5 , shall be determined in accordance with 
Section 208.6.4.1. To determine A M , these drifts shall be 
amplified in accordance with Section 208.6.4.2. 


208.6.4.1 Determination of A s 

A static, elastic analysis of the lateral force-resisting 
system shall be prepared using the design seismic forces 
from Section 208.5.2.1. Alternatively, dynamic analysis 
may be performed in accordance with Section 208.5.3. 
Where Allowable Stress Design is used and where drift is 
being computed, the load combinations of Section 203.3 
shall be used. The mathematical model shall comply with 
Section 208.6.2. The resulting deformations, denoted as 
A 5 , shall be determined at all critical locations in the 
structure. Calculated drift shall include translational and 
torsional deflections. 

208.6.4.2 Determination of A M 

The Maximum Inelastic Response Displacement, A M , shall 
be computed as follows: 

A m = 0. 7RA S (208-21) 

Exception: 

Alternatively , A m may be computed by nonlinear time 
history analysis in accordance with Section 208.5. 3.6.3. 

The analysis used to determine the Maximum Inelastic 
Response Displacement A M shall consider PA effects. 

208.6.5 Storey Drift Limitation 

Storey drifts shall be computed using the Maximum 
Inelastic Response Displacement, A M . 

208.6.5.1 Calculated 

Calculated storey drift using A M shall not exceed 0.025 
times the storey height for structures having a fundamental 
period of less than 0.7 sec. For structures having a 
fundamental period of 0.7 sec or greater, the calculated 
storey drift shall not exceed 0.020 times the storey height. 

Exceptions: 

1. These drift limits may be exceeded when it is 
demonstrated that greater drift can be tolerated by 
both structural elements and nonstructural elements 
that could affect life safety. The drift used in this 
assessment shall be based upon the Maximum 
Inelastic Response Displacement , A M . 

2. There shall be no drift limit in single-storey steel- 
framed structures whose primary use is limited to 
storage, factories or workshops. Minor accessory 
uses shall be allowed. Structures on which this 
exception is used shall not have equipment attached to 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-221 


the structural frame or shall have such equipment 
detailed to accommodate the additional drift . Walls 
that are laterally supported by the steel frame shall be 
designed to accommodate the drift in accordance with 
Section 208. 7.2.3 . 

208.6.5.2 Limitations 

The design lateral forces used to determine the calculated 
drift may disregard the limitations of Equations. 208-11 
and 208-10 and may be based on the period determined 
from Equations. 208-14 neglecting the 30 or 40 percent 
limitations of Section 208.5.2.2. 

208.6.6 Vertical Component 

The following requirements apply in Seismic Zone 4 only. 
Horizontal cantilever components shall be designed for a 
net upward force of 0. 7C a IW p . 

In addition to all other applicable load combinations, 
horizontal pre-stressed components shall be designed using 
not more than 50 percent of the dead load for the gravity 
load, alone or in combination with the lateral force effects. 

208.7 Detailed Systems Design Requirements 

208.7.1 General 

All structural framing systems shall comply with the 
requirements of Section 208.4. Only the elements of the 
designated seismic-force-resisting system shall be used to 
resist design forces. The individual components shall be 
designed to resist the prescribed design seismic forces 
acting on them. The components shall also comply with the 
specific requirements for the material contained in 
Chapters 4 through 7. In addition, such framing systems 
and components shall comply with the detailed system 
design requirements contained in Section 208.7. 

All building components in Seismic Zones 2 and 4 shall be 
designed to resist the effects of the seismic forces 
prescribed herein and the effects of gravity loadings from 
dead and floor live loads. 

Consideration shall be given to design for uplift effects 
caused by seismic loads. 


In Seismic Zones 2 and 4, provision shall be made for the 
effects of earthquake forces acting in a direction other than 
the principal axes in each of the following circumstances: 

1. The structure has plan irregularity Type 5 as given in 
Table 208-10. 

2. The structure has plan irregularity Type 1 as given in 
Table 208-10 for both major axes. 

3. A column of a structure forms part of two or more 
intersecting lateral-force-resisting systems. 

Exception: 

If the axial load in the column due to seismic forces acting 
in either direction is less than 20 percent of the column 
axial load capacity. 

The requirement that orthogonal effects be considered may 
be satisfied by designing such elements for 100 percent of 
the prescribed design seismic forces in one direction plus 
30 percent of the prescribed design seismic forces in the 
perpendicular direction. The combination requiring the 
greater component strength shall be used for design. 
Alternatively, the effects of the two orthogonal directions 
may be combined on a square root of the sum of the squares 
(SRSS) basis. When the SRSS method of combining 
directional effects is used, each term computed shall be 
assigned the sign that will result in the most conservative 
result. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


122 CHAPTER 2 - Minimum Design Loads 


8.7.2 Structural Framing Systems 

ur types of general building framing systems defined in 
ction 208.4.6 are recognized in these provisions and 
Dwn in Table 208-11. Each type is subdivided by the 
)es of vertical elements used to resist lateral seismic 
*ces. Special framing requirements are given in this 
:tion and in Chapters 4 through 7. 

8.7.2.1 Detailing for Combinations of Systems 

r components common to different structural systems, 
; more restrictive detailing requirements shall be used. 

8.7.2.2 Connections 

mnections that resist design seismic forces shall be 
signed and detailed on the drawings. 

8.7.2.3 Deformation Compatibility 

1 structural framing elements and their connections, not 
luired by design to be part of the lateral-force-resisting 
stem, shall be designed and/or detailed to be adequate to 
iintain support of design dead plus live loads when 
bjected to the expected deformations caused by seismic 
rces. PA effects on such elements shall be considered. 
;pected deformations shall be determined as the greater 


of the Maximum Inelastic Response Displacement, A Ms 
considering PAD effects determined in accordance with 
Section 208.6.4.2 or the deformation induced by a storey 
drift of 0.0025 times the storey height. When computing 
expected deformations, the stiffening effect of those 
elements not part of the lateral-force-resisting system shall 
be neglected. 

For elements not part of the lateral-force-resisting system, 
the forces inducted by the expected deformation may be 
considered as ultimate or factored forces. When computing 
the forces induced by expected deformations, the 
restraining effect of adjoining rigid structures and 
nonstructural elements shall be considered and a rational 
value of member and restraint stiffness shall be used. 
Inelastic deformations of members and connections may be 
considered in the evaluation, provided the assumed 
calculated capacities are consistent with member and 
connection design and detailing. 

For concrete and masonry elements that are part of the 
lateral- force-resisting system, the assumed flexural and 
shear stiffness properties shall not exceed one half of the 
gross section properties unless a rational cracked-section 
analysis is performed. Additional deformations that may 
result from foundation flexibility and diaphragm 
deflections shall be considered. For concrete elements not 
part of the lateral-force-resisting system, see Section 42 1 .9. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-223 


Table 208-1 1A Earthquake-Force-Resisting Structural Systems of Concrete 


Basic Seismic-Force Resisting System 

R 

n 0 

System Limitation and 
Building Height Limitation by 
Seismic Zone, m 



Zone 2 

Zone 4 

A. Bearing Wall Systems 





• Special reinforced concrete shear walls 

4.5 

2.8 

NL 

50 

• Ordinary reinforced concrete shear walls 

4.5 

2.8 

NL 

NP 

B. Building Frame Systems 





• Special reinforced concrete shear walls or braced 
frames (shear walls) 

5.0 

2.8 

NL 

75 

• Ordinary reinforced concrete shear walls or braced 
frames 

5.6 

2.2 

NL 

NP 

• Intermediate precast shear walls or braced frames 

5.0 

2.5 

NL 

10 

C. Moment-Resisting Frame Systems 





• Special reinforced concrete moment frames 

8.5 

2.8 

NL 

NL 

• Intermediate reinforced concrete moment frames 

5.5 

2.8 

NL 

NP 

• Ordinary reinforced concrete moment frames 

3.5 

2.8 

NL 

NP 

D . Dual Systems 





• Special reinforced concrete shear walls 

8.5 

2.8 

NL 

NL 

• Ordinary reinforced concrete shear walls 

6.5 

2.8 

NL 

NP 

E. Dual System with Intermediate Moment Frames 





• Special reinforced concrete shear walls 

6.5 

2.8 

NL 

50 

• Ordinary reinforced concrete shear walls 

5.5 

2.8 

NL 

NP 

• Shear wall frame interactive system with ordinary 
reinforced concrete moment frames and ordinary 
reinforced concrete shear walls 

4.2 

2.8 

NP 

NP 

F. Cantilevered Column Building Systems 





• Cantilevered column elements 

2.2 

2.0 

NL 

10 

G. Shear Wall- Frame Interaction Systems 

5.5 

2.8 

NL 

50 


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2-224 CHAPTER 2 - Minimum Design Loads 


Table 208-1 IB Earthquake-Force-Resisting Structural Systems of Steel 


Basic Seismic-Force Resisting System 

R 

n 0 

System Limitation and 
Building Height Limitation by 
Seismic Zone, m 

Zone 2 

Zone 4 

A. Bearing Wall Systems 





• Light steel-framed bearing walls with tension-only 
bracing 

2.8 

2.2 

NL 

20 

• Braced frames where bracing carries gravity load 

4.4 

2.2 

NL 

50 

• Light framed walls sheathed with steel sheets 
structural panels rated for shear resistance or steel 
sheets 

5.5 

2.8 

NL 

20 

• Light-framed walls with shear panels of all other 
light materials 

4.5 

2.8 

NL 

20 

• Light-framed wall systems using flat strap bracing 

2.8 

2.2 

NL 

NP 

B. Building Frame Systems 





• Steel eccentrically braced frames (EBF), moment- 
resist in g connections at columns away from links 

8.0 

2.8 

NL 

30 

* Steel eccentrically braced frames (EBF), non- 
moment-resisting connections at columns away 
from links 

6.0 

2.2 

NL 

30 

• Special concentrically braced frames (SCBF) 

6.0 

2.2 

NL 

30 

• Ordinary concentrically braced frames (OCBF) 

3.2 

2.2 

NL 

NP 

• Light-framed walls sheathed with steel sheet 
structural panels / sheet steel panels 

6.5 

2.8 

NL 

20 

• Light frame walls with shear panels of all other 
materials 

2.5 

2.8 

NL 

NP 

• Buckling-restrained braced frames (BRBF), non- 
moment-resisting beam-column connection 

7.0 

2.8 

NL 

30 

• Buckling-restrained braced frames, moment- 
resisting beam-column connections 

8.0 

2.8 

NL 

30 

• Special steel plate shear walls (SPSW) 

7.0 

2.8 

NL 

30 

C, Moment-Resisting Frame Systems 





• Special moment-resisting frame (SMRF) 

8.0 

3.0 

NL 

NL 

• Intermediate steel moment frames ( 1 Mb') 

4.5 

3.0 

NL 

NP 

• Ordinary moment frames (OMF) 

3.5 

3.0 

NL 

NP 

• Special truss moment frames (STMF) 

6.5 

3.0 

NL 

NP 

• Special composite steel and concrete moment 
frames 

8.0 

3.0 

NL 

NL 

• Intermediate composite moment frames 

5.0 

3.0 

NL 

NP 

• Composite partially restrained moment frames 

6.0 

3.0 

50 

NP 

• Ordinary composite moment frames 

3.0 

3.0 

NP 

NP 

D. Dual Systems with Special Moment Frames 





• Steel eccentrically braced frames 

8.0 

2.8 

NL 

NL 

• Special steel concentrically braced frames 

7.0 

2.8 

NL 

NL 

• Composite steel and concrete eccentrically braced 
frame 

8.0 

2.8 

NL 

NL 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-225 


Table 208-1 IB (continued) Earthquake-Force-Resisting Structural Systems of Steel 


Basic Seismic-Force Resisting System 

R 

I2 0 

System Limitation and 
Building Height 
Limitation by Seismic 
Zone, m 



Zone 2 

Zone 4 

• Composite steel and concrete concentrically braced 
frame 

6.0 

2.8 

NL 

NL 

• Composite steel plate shear walls 

7.5 

2.8 

NL 

NL 

• Buckling-restrained braced frame 

8.0 

2.8 

NL 

NL 

• Special steel plate shear walls 

8.0 

2.8 

NL 

NL 

• Masonry shear wall with steel OMRF 

4.2 

2.8 

NL 

50 

• Steel EBF with steel SMRF 

8.5 

2.8 

NL 

NL 

• Steel EBF with steel OMRF 

4.2 

2.8 

NL 

50 

• Special concentrically braced frames with steel 

SMRF 

7.5 

2.8 

NL 

NL 

• Special concentrically braced frames with steel 

OMRF 

4.2 

2.8 

NL 

50 

E. Dual System with Intermediate Moment Frames 





• Special steel concentrically braced frame 

6.0 

2.8 

NL 

NP 

• Composite steel and concrete concentrically braced 
frame 

5.5 

2.8 

NL 

NP 

• Ordinary composite braced frame 

3.5 

2.8 

NL 

NP 

• Ordinary composite reinforced concrete shear walls 
with steel elements 

5.0 

3.0 

NL 

NP 

F, Cantilevered Column Building Systems 





• Special steel moment frames 

2.2 

2.0 

10 

10 

• Intermediate steel moment frames 

1.2 

2.0 

10 

NP 

• Ordinary steel moment frames 

1.0 

2.0 

10 

NP 

• Cantilevered column elements 

2.2 

2.0 

NL 

10 

(7. Steel Systems not Specifically Detailed for Seismic 
Resistance , Excluding Cantilever Systems 

3.0 

3.0 

NL 

NP 


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Table 208-1 1C Earthquake-Force- Resisting Structural Systems of Masonry 


Basic Seismic-Force Resisting System 

R 

f2 0 

System Limitation and 
Building Height Limitation by 
Seismic Zone, m 

Zone 2 

Zone 4 

A. Bearing Wall Systems 





• Masonry shear walls 

4.5 

2.8 

NL 

50 

B . Building Frame Systems 





• Masonry shear walls 

5.5 

2.8 

NL 

50 

C. Moment-Resisting Frame Systems 





• Masonry moment-resisting wall frames (MMRWF) 

6.5 

2.8 

NL 

50 

D. Dual Systems 





• Masonry shear walls with SMRF 

5.5 

2.8 

NL 

50 

• Masonry shear walls with steel OMRF 

4.2 

2.8 

NL 

50 

• Masonry shear walls with concrete IMRF 

4.2 

2.8 

NL 

NP 

• Masonry shear walls with masonry MMRWF 

6.0 

2.8 

NL 

50 


Table 208-1 ID Earthquake-Force-Resisting Structural Systems of Wood 


Basic Seismic-Force Resisting System 

R 

n 0 

System Limitation and 
Building Height Limitation by 
Seismic Zone (meters) 



Zone 2 

Zone 4 

A. Bearing Wall Systems 





• Light-framed walls with shear panels: wood 

structural panel walls for structures three stories or 
less 

5.5 

2.8 

NL 

20 

• Heavy timber braced frames where bracing carries 
gravity load 

2.8 

2.2 

NL 

20 

• All other light framed walls 

NA 

NA 



B. Building Frame Systems 





• Ordinary heavy timber-braced frames 

5.6 

2.2 

* NL 

20 


208.7.2.3.1 Adjoining Rigid Elements 

Moment-resisting frames and shear walls may be enclosed 
by or adjoined by more rigid elements; provided it can be 
shown that the participation or failure of the more rigid 
elements will not impair the vertical and lateral- load- 
resisting ability of the gravity load and lateral-force- 
resisting systems. The effects of adjoining rigid elements 
shall be considered when assessing whether a structure 
shall be designated regular or irregular in Section 208.4.5. 

208.7.2.3.2 Exterior Elements 

Exterior non-bearing, non-shear wall panels or elements 
that are attached to or enclose the exterior shall be designed 
to resist the forces per Equation 208-27 or 208-28 and shall 
accommodate movements of the structure based on and 
temperature changes. Such elements shall be supported by 
means of cast-in-place concrete or by mechanical 


connections and fasteners in accordance with the following 
provisions: 

1. Connections and panel joints shall allow for a relative 
movement between stories of not less than two times 
storey drift caused by wind, the calculated storey drift 
based on or 12.7 mm, whichever is greater. 

2. Connections to permit movement in the plane of the 
panel for storey drift shall be sliding connections using 
slotted or oversize holes, connections that permit 
movement by bending of steel, or other connections 
providing equivalent sliding and ductility capacity. 

3. Bodies of connections shall have sufficient ductility 
and rotation capacity to preclude fracture of the 
concrete or brittle failures at or near welds. 


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CHAPTER 2 - Minimum Design Loads 2-227 


other elements of the lateral-force-resisting system. For 
Allowable Stress Design, the design strength may be 
determined using an allowable stress increase of 1.7 and a 
resistance factor, 0 , of 1.0. This increase shall not be 
combined with the one-third stress increase permitted by 
Section 203.4, but may be combined with the duration of 
load increase permitted in Section 615.3.4. 

208.7.2.5 Concrete Frames 

Concrete frames required by design to be part of the lateral- 
force-resisting system shall conform to the following: 


4. The body of the connection shall be designed for the 
force determined by Equation 208-28, where R p = 

3. 0 and a p = 1. 0. 

5. All fasteners in the connecting system, such as bolts, 
inserts, welds and dowels, shall be designed for the 
forces determined by Equation 208-28, where R p = 

1. 0 and a p = 1. 0. 

6. Fasteners embedded in concrete shall be attached to, 
or hooked around, reinforcing steel or otherwise 
terminated to effectively transfer forces to the 
reinforcing steel. 


208.7.2.3.3 Ties and Continuity 

All parts of a structure shall be interconnected and the 
connections shall be capable of transmitting the seismic 
force induced by the parts being connected. As a minimum, 
any smaller portion of the building shall be tied to the 
remainder of the building with elements having at least 
strength to resist 0. 5C a I times the weight of the smaller 
portion. 

A positive connection for resisting horizontal force acting 
parallel to the member shall be provided for each beam, 
girder or truss. This force shall not be less than 0.3C a 7 
times the dead plus live load. 

208.7.2.4 Collector Elements 

Collector elements shall be provided that are capable of 
transferring the seismic forces originating in other portions 
of the structure to the element providing the resistance to 
those forces. 

Collector elements, splices and their connections to 
resisting elements shall resist the forces determined in 
accordance with Equation 208-22. In addition, collector 
elements, splices, and their connections to resisting 
elements shall have the design strength to resist the 
combined loads resulting from the special seismic load of 
Section 203.5. 

Exception: 

In structures, or portions thereof, braced entirely by light- 
frame wood shear walls or light-frame steel and wood 
structural panel shear wall systems, collector elements, 
splices and connections to resisting elements need only be 
designed to resist forces in accordance with Equation 208- 
22 . 

The quantity E M need not exceed the maximum force that 
can be transferred to the collector by the diaphragm and 


1. In Seismic Zone 4 they shall be special moment- 
resisting frames. 

2. In Seismic Zone 2 they shall, as a minimum, be 
intermediate moment-resisting frames. 

208.7.2.6 Anchorage of Concrete or Masonry Walls 

Concrete or masonry walls shall be anchored to all floors 
and roofs that provide out-of-plane lateral support of the 
wall. The anchorage shall provide a positive direct 
connection between the wall and floor or roof construction 
capable of resisting the larger of the horizontal forces 
specified in this section and Sections 206.4 and 208.9. In 
addition, in Seismic Zone 4, diaphragm to wall anchorage 
using embedded straps shall have the straps attached to or 
hooked around the reinforcing steel or otherwise 
terminated to effectively transfer forces to the reinforcing 
steel. Requirements for developing anchorage forces in 
diaphragms are given in Section 208.7.2.6. Diaphragm 
deformation shall be considered in the design of the 
supported walls. 

208.7.2.6.1 Out-of-Plane Wall Anchorage to 
Flexible Diaphragms 

This section shall apply in Seismic Zone 4 where flexible 
diaphragms, as defined in Section 208.5. 1 .3, provide lateral 
support for walls. 

1. Elements of the wall anchorage system shall be 
designed for the forces specified in Section 208.9 
where R p = 3. 0 and a p = 1. 5. 

2. In Seismic Zone 4, the value of F p used for the design 
of the elements of the wall anchorage system shall not 
be less than 6. 1 kN per lineal meter of wall substituted 
for E. 

3. See Section 206.4 for minimum design forces in other 
seismic zones. 


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2-228 CHAPTER 2 - Minimum Design Loads 


4. When elements of the wall anchorage system are not 
loaded concentrically or are not perpendicular to the 
wall, the system shall be designed to resist all 
components of the forces induced by the eccentricity. 

5. When pilasters are present in the wall, the anchorage 
force at the pilasters shall be calculated considering 
the additional load transferred from the wall panels to 
the pilasters. However, the minimum anchorage force 
at a floor or roof shall be that specified in Section 
208.7.2.7, Item 2. 

6. The strength design forces for steel elements of the 
wall anchorage system shall be 1 .4 times the forces 
otherwise required by this section. 

7. The strength design forces for wood elements of the 
wall anchorage system shall be 0.85 times the force 
otherwise required by this section and these wood 
elements shall have a minimum actual net thickness of 
63.5 mm. 


accordance with Section 208.5.2 using a R no ^ 
exceeding 4. 

4. Diaphragms supporting concrete or masonry walls 
shall have continuous ties or struts between diaphragm 
chords to distribute the anchorage forces specified in 
Section 208.7.2.7. Added chords of subdiaphragms 
may be used to form subdiaphragms to transmit the 
anchorage forces to the main continuous crossties. The 
maximum length-to-width ratio of the wood structural 
sub-diaphragm shall be 2 l A:l. 

5. Where wood diaphragms are used to laterally support 
concrete or masonry walls, the anchorage shall 
conform to Section 208.7.2.7. In Seismic Zone 2 and 
4, anchorage shall not be accomplished by use of 
toenails or nails subject to withdrawal, wood ledgers 
or framing shall not be used in cross-grain bending or 
cross-grain tension, and the continuous ties required 
by Item 4 shall be in addition to the diaphragm 
sheathing. 


208.7.2.7 Diaphragms 

1 . The deflection in the plane of the diaphragm shall not 
exceed the permissible deflection of the attached 
elements. Permissible deflection shall be that 
deflection that will permit the attached element to 
maintain its structural integrity under the individual 
loading and continue to support the prescribed loads. 

2. Floor and roof diaphragms shall be designed to resist 
the forces determined in accordance with the 
following equation: 


F 

1 px 


Iu=x w i 


Ft 

— Wpx 


(208-22) 


The force F px determined from Equation 208-22 need 
not exceed 1.0 C a Iw px , but shall not be less than 

0 . 5C a Iw px . 

When the diaphragm is required to transfer design 
seismic forces from the vertical-resisting elements 
above the diaphragm to other vertical-resisting 
elements below the diaphragm due to offset in the 
placement of the elements or to changes in stiffness in 
the vertical elements, these forces shall be added 
to those determined from Equation 208-22. 


6. Connections of diaphragms to the vertical elements in 
structures in Seismic Zone 4, having a plan irregularity 
of Type 1, 2, 3 or 4 in Table 208-10, shall be designed 
without considering either the one-third increase or the 
duration of load increase considered in allowable 
stresses for elements resisting earthquake forces. 

7. In structures in Seismic Zone 4 having a plan 
irregularity of Type 2 in Table 208-10, diaphragm 
chords and drag members shall be designed 
considering independent movement of the projecting 
wings of the structure. Each of these diaphragm 
elements shall be designed for the more severe of the 
following two assumptions: 

a. Motion of the projecting wings in the same 
direction. 

b. Motion of the projecting wings in opposing 
directions. 

Exception: 

This requirement may be deemed satisfied if the procedures 
of Section 208,5.3 in conjunction with a three-dimensional 
model have been used to determine the lateral seismic 
forces for design. 

208.7.2.8 Framing below the Base 


3. Design seismic forces for flexible diaphragms 
providing lateral supports for walls or frames of 
masonry or concrete shall be determined using 
Equation 208-22 based on the load determined in 


The strength and stiffness of the framing between the base 
and the foundation shall not be less than that of the 
superstructure. The special detailing requirements of 
Chapters 4, 5 and 7, as appropriate, shall apply to columns 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-229 


supporting discontinuous lateral-force-resisting elements 
and to SMRF, IMRF, EBF, STMF and MMRWF system 
elements below the base, which are required to transmit the 
forces resulting from lateral loads to the foundation. 

208.7.2.9 Building Separations 

All structures shall be separated from adjoining structures. 
Separations shall allow for the displacement A m . Adjacent 
buildings on the same property shall be separated by at 
least A MT where 


A mt — V (A M i) + (A M2 ) 2 (208-23) 

and A M1 and A M2 are the displacements of the adjacent 
buildings. 

When a structure adjoins a property line not common to a 
public way, that structure shall also be set back from the 
property line by at least the displacement A M of that 
structure. 

Exception: 

Smaller separations or property line setbacks may be 
permitted when justified by rational analyses based on 
maximum expected ground motions. 

208.8 Non-Building Structures 

208.8.1 General 

208.8.1.1 Scope 

Non-building structures include all self- supporting 
structures other than buildings that carry gravity loads and 
resist the effects of earthquakes. Non-building structures 
shall be designed to provide the strength required to resist 
the displacements induced by the minimum lateral forces 
specified in this section. Design shall conform to the 
applicable provisions of other sections as modified by the 
provisions contained in Section 208.8. 

208.8.1.2 Criteria 


When applicable, design strengths and other detailed 
design criteria shall be obtained from other sections or their 
referenced standards. The design of non-building 
structures shall use the load combinations or factors 
specified in Section 203.3 or 203.4. For non-building 
structures designed using Section 208.8.3, 208.8.4 or 
208.8.5, the Reliability/Redundancy Factor, p, may be 
taken as 1.0. 

When applicable design strengths and other design criteria 
are not contained in or referenced by this code, such criteria 
shall be obtained from approved national standards. 

208.8.1.3 Weight W 

The weight, W, for non-building structures shall include all 
dead loads as defined for buildings in Section 208.6.1. For 
purposes of calculating design seismic forces n non- 
building structures, W shall also include all normal 
operating contents for items such as tanks, vessels, bins and 
piping. 

208.8.1.4 Period 

The fundamental period of the structure shall be 
determined by rational methods such as by using Method 
B in Section 208.5.2.2. 

208.8.1.5 Drift 

The drift limitations of Section 208.6.5 need not apply to 
non-building structures. Drift limitations shall be 
established for structural or nonstructural elements whose 
failure would cause life hazards. PA effects shall be 
considered for structures whose calculated drifts exceed 
the values in Section 208.6.3. 


The minimum design seismic forces prescribed in this 
section are at a level that produces displacements in a fixed 
base, elastic model of the structure, comparable to those 
expected of the real structure when responding to the 
Design Basis Ground Motion. Reductions in these forces 
using the coefficient R is permitted where the design of 
non-building structures provides sufficient strength and 
ductility, consistent with the provisions specified herein for 
buildings, to resist the effects of seismic ground motions as 
represented by these design forces. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-230 CHAPTER 2 - Minimum Design Loads 


Table 208-12 R and ft on Factors for Non-building 
Structures 


STRUCTURE TYPE 

R 


1 . Vessels, including tanks and 
pressurized spheres, on braced 
or unbraced legs. 

2.2 

2.0 

2. Cast-in-place concrete silos and 
chimneys having walls 
continuous to the foundations 

3.6 

2.0 

3. Distributed mass cantilever 
structures such as stacks, 
chimneys, silos and skirt- 
supported vertical vessels. 

2.9 

2.0 

4. Trussed towers (freestanding or 
guyed), guyed stacks and 
chimneys. 

2.9 

2.0 

5. Cantilevered column-type 
structures. 

2.2 

2.0 

6. Cooling towers. 

3.6 

2.0 

7. Bins and hoppers on braced or 
unbraced legs. 

2.9 

2.0 

8. Storage racks. 

3.6 

2.0 

9. Signs and billboards. 

3.6 

2.0 

10. Amusement structures and 
monuments. 

2.2 

2.0 

1 1. All other self-supporting 

structures not otherwise covered. 

2.9 

2.0 


208.8.1.6 Interaction Effects 

In Seismic Zone 4, structures that support flexible 
nonstructural elements whose combined weight exceeds 25 
percent of the weight of the structure shall be designed 
considering interaction effects between the structure and 
the supported elements. 

208.8.2 Lateral Force 


calculated member forces and moments does not exceed 

2 . 8 . 

208.8.3 Rigid Structures 

Rigid structures (those with period T less than 0.06 s) and 
their anchorages shall be designed for the lateral force 
obtained from Equation 208-24. 

V = 0.7C a IW (208-24) 

The force V shall be distributed according to the 
distribution of mass and shall be assumed to act in any 
horizontal direction. 

208.8.4 Tanks with Supported Bottoms 

Flat bottom tanks or other tanks with supported bottoms, 
founded at or below grade, shall be designed to resist the 
seismic forces calculated using the procedures in Section 
208.9 for rigid structures considering the entire weight of 
the tank and its contents. Alternatively, such tanks may be 
designed using one of the two procedures described below: 

1 . A response spectrum analysis that includes 
consideration of the actual ground motion anticipated 
at the site and the inertial effects of the contained fluid. 

2. A design basis prescribed for the particular type of 
tank by an approved national standard, provided that 
the seismic zones and occupancy categories shall be in 
conformance with the provisions of Sections 208.4.4.2 
and 208.4.4.3, respectively. 

208.8.5 Other Non-building Structures 

Non-building structures that are not covered by Section 
208.8.3 and 208.8.4 shall be designed to resist design 
seismic forces not less than those determined in accordance 
with the provisions in Section 208.5 with the following 
additions and exceptions: 


Lateral-force procedures for non-building structures with 
structural systems similar to buildings (those with 
structural systems which are listed in Table 208-11) shall 
be selected in accordance with the provisions of Section 
208.4. 


1 . The factors R and ft 0 shall be as set forth in Table 
208-12. The total design base shear determined in 
accordance with Section 208.5.2 shall not be less than 
the following: 

V = 0. 56 C a IW (208-25) 


Exception: 

Intermediate moment-resisting frames (IMRF) may be used 
in Seismic Zone 4 for non-building structures in 
Occupancy Categories III and IV if (1) the structure is less 
than 15 m in height and (2) the value R used in reducing 


Additionally, for Seismic Zone 4, the total base shear 
shall also not be less than the following: 


1.6 ZNJ 


(208-26) 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 


2 231 


2. The vertical distribution of the design seismic forces 
in structures covered by this section may be 
determined by using the provisions of Section 
208.5.2.3 or by using the procedures of Section 
208.5.3. 


208.9.2 Design for Total Lateral Force 

The total design lateral seismic force, F p , shall be 
determined from the following equation: 


Fp 4C a I p w p 


(208-27) 


Exception: 

For irregular structures assigned to Occupancy 
Categories I and II that cannot be modeled as a single 
mass , the procedures of Section 208.5.3 shall be used . 

3. Where an approved national standard provides a basis 
for the earthquake-resistant design of a particular type 
of non-building structure covered by this section, such 
a standard may be used, subject to the limitations in 
this section: 

The seismic zones and occupancy categories shall be in 
conformance with the provisions of Sections 208.4.4 and 
208.4.2, respectively. 

The values for total lateral force and total base overturning 
moment used in design shall not be less than 80 percent of 
the values that would be obtained using these provisions. 

208.9 Lateral Force on Elements of Structures, 
Nonstructural Components and Equipment 
Supported by Structures 

208.9.1 General 

Elements of structures and their attachments, permanent 
nonstructural components and their attachments, and the 
attachments for permanent equipment supported by a 
structure shall be designed to resist the total design seismic 
forces prescribed in Section 208.9.2. 

Attachments for floor- or roof-mounted equipment 
weighing less than 1.8 kN, and furniture need not be 
designed. 

Attachments shall include anchorages and required 
bracing. Friction resulting from gravity loads shall not be 
considered to provide resistance to seismic forces. 

When the structural failure of the lateral-force-resisting 
systems of non-rigid equipment would cause a life hazard, 
such systems shall be designed to resist the seismic forces 
prescribed in Section 208.9.2. 

When permissible design strengths and other acceptance 
criteria are not contained in or referenced by this code, such 
criteria shall be obtained from approved national standards 
subject to the approval of the building official. 


Alternatively, F p may be calculated using the following 
equation: 

tipCJp ( h x \ 

F r’ = \ L [ 1 + 3 f y ) W <> ^ 208 - 28 ) 

Except that F p shall not be less than 0. 7 C a I p W p and need 
not be more than 4C a I p W p . 

where 

h x = the element or component attachment 
elevation with respect to grade. 
h x shall not be taken less than 0.0. 
h r = the structure roof elevation with respect to 
grade. 

a p = the in-structure Component Amplification 
Factor that varies from 1 .0 to 2.5, 

A value for a p shall be selected from Table 208-13. 
Alternatively, this factor may be determined based on the 
dynamic properties or empirical data of the component and 
the structure that supports it. The value shall not be taken 
less than 1.0. 

R p is the Component Response Modification Factor that 
shall be taken from Table 208-13, except that R p for 
anchorages shall equal 1 .5 for shallow expansion anchor 
bolts, shallow chemical anchors or shallow cast-in-place 
anchors. Shallow anchors are those with an embedment 
length-to-diameter ratio of less than 8. When anchorage is 
constructed of non-ductile materials, or by use of adhesive, 
R p shall equal 1 .0. 

The design lateral forces determined using Equation 208- 
27 or 208-19 shall be distributed in proportion to the mass 
distribution of the element or component. 


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2-232 CHAPTER 2 - Minimum Design Loads 


Forces determined using Equation 208-27 or 208-28 shall 
be used to design members and connections that transfer 
th&e forces to the seismic-resisting systems. Members and 
connection design shall use the load combinations and 
factors specified in Section 203.3 or 203.4. The 
Reliability/Redundancy Factor, p, may be taken equal to 
1 . 0 . 

For applicable forces and Component Response 
Modification Factors in connectors for exterior panels and 
diaphragms, refer to Sections 208.7.2.3 and 208.7.2.7. 

Forces shall be applied in the horizontal directions, which 
result in the most critical loadings for design. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-233 


Table 208-13 Horizontal Force Factors, a p and R p for 
Elements of Structures and Nonstructural Components 
and Equipment 


Category 

Element or 
Component 

CLp 

R P 

Footnote 

1. Elements of 
Structures 

1 . Walls including the following 

a. Unbraced 
(cantilevered) 
parapets 

2.5 

3.0 


b. Exterior walls 
at or above the 
ground floor 
and parapets 
braced above 
their centers 
of gravity 

1.0 

3.0 

2 

c. All interior- 
bearing and 
non-bearing 
walls 

1.0 

3.0 

2 

2. Penthouse 
(except when 
framed by an 
extension of 
the structural 
frame) 

2.5 

4.0 


3. Connections 
for 

prefabricated 
structural 
elements other 
walls. See also 
Section 

208.7.2 

1.0 

3.0 

3 


Table 208-13 (continued) 


Category 

Element or 
Component 

d p 

R P 

Footnote 

2. 

i Nonstructural 
Components 

1 . Exterior and interior ornamentations 
and appendages. 

a. Laterally 
braced or 
anchored to 
the structural 
frame at a 
point below 
their centers 
of mass 

2.5 

3.0 


b. Laterally 
braced or 
anchored to 
the structural 
frame at or 
above their 
centers of 

mass 

1.0 

3.0 


2. Signs and 
billboards 

2.5 

3.0 


3. Storage racks 
(include 
contents) over 
1.8 m tall. 

2.5 

4.0 

4 

4. Permanent 
floor- 
supported 
cabinets and 
book stacks 
more than 1.8 
m in height 
(include 
contents) 

1.0 

3.0 

5 

5. Anchorage 
and lateral 
bracing for 
suspended 
ceilings and 
light fixtures 

1.0 

3.0 

3, 6, 7, 

8 

6. Access floor 
systems 

1.0 

3.0 

4 , 5, 9 

7. Masonry or 
concrete 
fences over 

1.8 m high 

1.0 

3.0 


8. Partitions. 

1.0 

3.0 



National Structural Code of the Philippines Volume l p 7th Edition, 2015 


2-234 CHAPTER 2 - Minimum Design Loads 


Table 208-13 (continued) 


.Category 

Element or 
Component 

a p 

R P 

Footnote 

3. Equipment 

1 . Tanks and 
vessels 
(include 
contents), 
including 
support 
systems. 

1.0 

3.0 


2. Electrical, 
mechanical 
and plumbing 
equipment and 
associated 
conduit and 
ductwork and 
piping. 

1.0 

3.0 

5 , 10, 

If 12, 
13, 14, 
15, 16 

3. Any flexible 
equipment 
laterally 
braced or 
anchored to 
the structural 
frame at a 
point below 
their center of 

mass 

2.5 

3.0 

5, 10, 

14 , 

15, 16 

4.Anchorage of 
emergency 
power supply 
systems and 
essential 
communicatio 
ns equipment. 
Anchorage 
and support 
systems for 
battery racks 
and fuel tanks 
necessary for 
operation of 
emergency 
equipment. 

See also 

Section 

208.7.2 

1.0 

3.0 

17, 18 

5. Temporary 
containers 
with 

flammable or 

hazardous 

materials. 

1.0 

3.0 

19 


Table 208-13 (continued) 


Category 

Element or 
Component 

CLp 

R P 

Footnote 

4. Other 
Components 

1 . Rigid 
components 
with ductile 
material and 
attachments. 

1.0 

3.0 

_ — - 

1 

2. Rigid 
components 
with 

nonductile 
material or 
attachments 

1.0 

1.5 

1 

3. Flexible 
components 
with ductile 
material and 
attachments. 

2.5 

3.0 

1 

4. Flexible 
components 
with 

nonductile 
material or 
attachments. 

2.5 

1.5 

1 


Notes for Table 208.13 

1 See Section 208.2 for definitions of flexible components 
and rigid components. 

2 See Section 208.8. 7.2.3 and 208. 7.2. 7 for concrete and 
masonry walls and Section 208.9.2 for connections for 
panel connectors for panels. 

3 Applies to Seismic Zones 2 and 4 only. 

4 Ground supported steel storage racks may be designed 
using the provisions of Sections 208.8. Load and 
resistance factor design may be used for the design of 
cold-formed steel members, provided seismic design 
forces are equal to or greater than those specified in 
Section 208.9.2 or 208.8.3 as appropriate. 

5 Only anchorage or restraints need be designed. 

6 Ceiling weight shall include all light fixtures and other 
equipment or partitions that are laterally supported by 
the ceiling. For purposes of determining the seismic 
force, a ceiling weight of not less than 0.2 kPa shall be 
used. 

7 Ceilings constructed of lath and plaster or gypsum 
board screw or nail attached to suspended members 
that support a ceiling at one level extending from wall 
to wall need not be analyzed, provided the walls are not 
over 15 meters apart. 

8 Light fixtures and mechanical services installed in 
metal suspension systems for acoustical tile and lay-in 
panel ceilings shall be independently supported from 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




CHAPTER 2 - Minimum Design Loads 2-235 


the structure above as specified in UBC Standard 25-2, 
Part III 

9 Wp for access floor systems shall be the dead load of 
the access floor system plus 25 percent of the floor live 
load plus a 0.5 kPa partition load allowance. 

10 Equipment includes , but is not limited to, boilers, 
chillers, heat exchangers, pumps, air-handling units, 
cooling towers, control panels, motors, switchgear, 
transformers and life-safety equipment. It shall include 
major conduit, ducting and piping, which services such 
machinery and equipment and fire sprinkler systems. 
See Section 208.9.2 for additional requirements for 
determining a p for nonrigid or flexibly mounted 
equipment. 

11 Seismic restraints may be omitted from piping and duct 
supports if all the following conditions are satisfied: 

11 1 Lateral motion of the piping or duct will not cause 
damaging impact with other systems. 

112 The piping or duct is made of ductile material with 
ductile connections. 

113 Lateral motion of the piping or duct does not cause 
impact of fragile appurtenances (e.g., sprinkler heads) 
with any other equipment, piping or structural member. 

11 4 Lateral motion of the piping or duct does not cause 
loss of system vertical support. 

u 5 Rod-hung supports of less than 300 mm in length 
have top connections that cannot develop moments. 

11 6 Support members cantilevered up from the floor are 
checked for stability. 

12 Seismic restraints may be omitted from electrical 
raceways, such as cable trays, conduit and bus ducts, if 
all the following conditions are satisfied: 

12 1 Lateral motion of the raceway will not cause 
damaging impact with other systems. 

12 2 Lateral motion of the raceway does not cause loss of 
system vertical support. 

]2J Rod-hung supports of less than 300 mm in length 
have top connections that cannot develop moments. 

124 Support members cantilevered up from the floor are 
checked for stability. 

13 Piping, ducts and electrical raceways, which must be 
functional following an earthquake, spanning between 
different buildings or structural systems shall be 
sufficiently flexible to withstand relative motion of 
support points assuming out-of phase motions. 

14 Vibration isolators supporting equipment shall be 
designed for lateral loads or restrained from displacing 
laterally by other means. Restraint shall also be 
provided, which limits vertical displacement, such that 
lateral restraints do not become disengaged. a p and 
R p for equipment supported on vibration isolators shall 
be taken as 2.5 and 1.5, respectively, except that if the 
isolation mounting frame is supported by shallow or 

National Structural Code of the I 


expansion anchors, the design forces for the anchors 
calculated by Equations. 208-27, or 208-28 (including 
limits), shall be additionally multiplied by factor of 2. 0. 

15 Equipment anchorage shall not be designed such that 
loads are resisted by gravity friction (e.g., friction 
clips). 

16 Expansion anchors, which are required to resist 
seismic loads in tension, shall not be used where 
operational vibrating loads are present. 

17 Movement of components within electrical cabinets, 
rack-and skid-mounted equipment and portions of skid- 
mounted electromechanical equipment that may cause 
damage to other components by displacing, shall be 
restricted by attachment to anchored equipment or 
support frames. 

18 Batteries on racks shall be restrained against 
movement in all direction due to earthquake forces. 

19 Seismic restraints may include straps, chains, bolts, 
barriers or other mechanisms that prevent sliding, 
falling and breach of containment of flammable and 
toxic materials . Friction forces may not be used to resist 
lateral loads in the restraints unless positive uplift 
restraint is provided which ensures that the friction 
forces act continuously. 

208.9.3 Specifying Lateral Forces 

Design specifications for equipment shall either specify the 
design lateral forces prescribed herein or reference these 
provisions. 

208.9.4 Relative Motion of Equipment Attachments 

For equipment in Categories I and II buildings as defined 
in Table 103-1, the lateral-force design shall consider the 
effects of relative motion of the points of attachment to the 
structure, using the drift based upon A M . 

208.9.5 Alternative Designs 

Where an approved national standard or approved physical 
test data provide a basis for the earthquake-resistant design 
of a particular type of equipment or other nonstructural 
component, such a standard or data may be accepted as a 
basis for design of the items with the following limitations: 

1. These provisions shall provide minimum values for 
the design of the anchorage and the members and 
connections that transfer the forces to the seismic- 
resisting system. 

2. The force, F p , and the overturning moment used in the 
design of the nonstructural component shall not be less 
than 80 percent of the values that would be obtained 
using these provisions. 

les Volume I, 7th Edition, 2015 


2-236 


CHAPTER 2 - Minimum Design Loads 


208.10 Alternative Earthquake Load Procedure 

The earthquake load procedure of latest edition of 
ASCE/SEI 7 prior to the release of this code may be used 
in determining the earthquake loads as an alternative 
procedure subject to reliable research work commissioned 
by the owner or the engineer-on-record to provide for all 
data required due to the non-availability of PHIVOLCS- 
issued spectral acceleration maps for all areas in the 
Philippines. 

The engineer-on-record shall be responsible for the 
spectral acceleration and other related data not issued by 
PHIVOLCS used in the determination of the earthquake 
loads. This alternative earthquake load procedure shall be 
subject to Peer Review and approval of the Building 
Official. 


SECTION 209 

SOIL LATERAL LOADS 

209.1 General 

Basement, foundation and retaining walls shall be designed 
to resist lateral soil loads. Soil loads specified in Table 209- 
1 shall be used as the minimum design lateral soil loads 
unless specified otherwise in a soil investigation report 
approved by the building official. Basement walls and 
other walls in which horizontal movement is restricted at 
the top shall be designed for at-rest pressure. Retaining 
walls free to move and rotate at the top are permitted to be 
designed for active pressure. Design lateral pressure from 
surcharge loads shall be added to the lateral earth pressure 
load. Design lateral pressure shall be increased if soils with 
expansion potential are present at the site. 

Exception: 

Basement walls extending not more than 2,4 m below grade 
and supporting flexible floor systems shall be permitted to 
be designed for active pressure. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-237 


Table 209-1 - Soil Lateral Load 


Description of 
Backfill Material 

c 

Unified 

Soil 

Classificat 

ion 

Design Lateral 

Soil Load a 
kPa per m depth 

Active 

pressure 

At-rest 

pressure 

Well-graded, 
clean gravels; 
gravel-sand mixes 

GW 

5 

10 

Poorly graded 
clean gravels; 
gravel-sand mixes 

GP 

5 

10 

Silty gravels, 
poorly graded 
gravel-sand mixes 

GM 

6 

10 

Clayey gravels, 
poorly graded 
gravel-and-clay 
mixes 

GC 

7 

10 

Well-graded, 
clean sands; 
gravelly sand 
mixes 

SW 

5 

10 

Poorly graded 
clean sands; sand- 
gravel mixes 

SP 

5 

10 

Silty sands, poorly 
graded sand-silt 
mixes 

SM 

7 

10 

Sand-silt clay mix 
with plastic fines 

SM-SC 

7 

16 

Clayey sands, 
poorly graded 
sand-clay mixes 

SC 

10 

16 

Inorganic silts and 
clayey silts 

ML 

7 

16 

Mixture of 
inorganic silt and 
clay 

ML-CL 

10 

16 

Inorganic clays of 
low to medium 
plasticity 

CL 

10 

16 

Organic silts and 
silt clays, low 
plasticity 

OL 

Note b 

Note b 

Inorganic clayey 
silts, elastic silts 

MH 

Note b 

Note b 

Inorganic clays of 
high plasticity 

CH 

Note b 

Note b 

Organic clays and 
silty clays 

OH 

Note b 

Note b 


govern. Submerged or saturated soil pressures 
shall include the weight of the buoyant soil plus 
the hydrostatic loads . 

Unsuitable as backfdl material. 

The definition and classification of soil 
materials shall be in accordance with ASTM 
D2487. 


a Design lateral soil loads are given for moist 
conditions for the specified soils at their 
optimum densities. Actual field conditions shall 

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2-238 CHAPTER 2 - Minimum Design Loads 


SECTION 210 
RAIN LOADS 

/ 

210.1 Roof Drainage 

Roof drainage systems shall be designed in accordance 
with the provisions of the code having jurisdiction in the 
area. The flow capacity of secondary (overflow) drains or 
scuppers shall not be less than that of the primary drains or 
scuppers. 

210.2 Design Rain Loads 

Each portion of a roof shall be designed to sustain the load 
of rainwater that will accumulate on it if the primary 
drainage system for that portion is blocked plus the 
uniform load caused by water that rises above the inlet of 
the secondary drainage system at its design flow. 

R = 0.009(8d s + d h ) (210-1) 

where 

d h = additional depth of water on the undeflected 
roof above the inlet of secondary drainage 
system at its design flow (i.e., the hydraulic 
head), mm 

d s = depth of water on the undeflected roof up to 
the inlet of secondary drainage system when 
the primary drainage system is blocked (i.e., 
the static head), mm 

R = rain load on the undeflected roof, kPa 

When the phrase “undeflected roof’ is used, deflections 
from loads (including dead loads) shall not be considered 
when determining the amount of rain on the roof. 

210.3 Ponding Instability 

For roofs with a slope less than 6 mm per 300 mm, the 
design calculations shall include verification of adequate 
stiffness to preclude progressive deflection. 

210.4 Controlled Drainage 

Roofs equipped with hardware to control the rate of 
drainage shall be equipped with a secondary drainage 
system at a higher elevation that limits accumulation of 
water on the roof above that elevation. Such roofs shall be 
designed to sustain the load of rainwater that will 
accumulate on them to the elevation of the secondary 
drainage system plus the uniform load caused by water that 
rises above the inlet of the secondary drainage system at its 
design flow determined from Section 210.2. Such roofs 
shall also be checked for ponding instability in accordance 
with Section 210.3. 


SECTION 211 
FLOOD LOADS 

211.1 General 

Within flood hazard areas as established in Section 21 1.3, 
all new construction of buildings, structures and portions 
of buildings and structures, including substantial 
improvement and restoration of substantial damage to 
buildings and structures, shall be designed and constructed 
to resist the effects of flood hazards and flood loads. For 
buildings that are located in more than one flood hazard 
area, the provisions associated with the most restrictive 
flood hazard area shall apply. 

211.2 Definitions 

The following words and terms shall, for the purposes of 
this section, have the meanings shown herein. 

BASE FLOOD refers to flood having a 1 -percent chance 
of being equaled or exceeded in any given year. 

BASE FLOOD ELEVATION (BFE) is the elevation of 
the base flood, m, including wave height, relative to the 
datum to be set by the specific national or local government 
agency. 

BASEMENT is the portion of a building having its floor 
subgrade (below ground level) on all sides. 

DESIGN FLOOD is the flood associated with the greater 
of the following two areas: 

1 . Area with a flood plain subject to a 1 -percent or greater 
chance of flooding in any year; or 

2. Area designated as a flood hazard area on a 
community’s flood hazard map, or otherwise legally 
designated. 

DESIGN FLOOD ELEVATION (DFE) is the elevation 
of the “design flood,” including wave height, m, relative to 
the datum specified on the community’s legally designated 
flood hazard map. The design flood elevation shall be the 
elevation of the highest existing grade of the perimeter of 
the building plus the depth specified on the flood hazard 
map. 

DRY FLOODPROOFING is a combination of design 
modifications that results in a building or structure, 
including the attendant utility and sanitary facilities, being 
water tight with walls substantially impermeable to the 
passage of water and with structural components having 
the capacity to resist loads as identified in the code. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-239 


EXISTING CONSTRUCTION refers to buildings and 
structures for which the “start of construction” commenced 
before the effective date of the ordinance or standard. 
“Existing construction” is also referred to as “existing 
structures.” 

EXISTING STRUCTURE See “Existing construction.” 

FLOOD or FLOODING is a general and temporary 
condition of partial or complete inundation of normally dry 
land from: 

1 . The overflow of inland or tidal waters. 

2. The unusual and rapid accumulation or runoff of 
surface waters from any source. 

FLOOD DAMAGE-RESISTANT MATERIALS are 

construction material capable of withstanding direct and 
prolonged contact with floodwaters without sustaining any 
damage that requires more than cosmetic repair. 

FLOOD HAZARD AREA refers to the greater of the 
following two areas: 

1 . The area within a flood plain subject to a 1 -percent or 
greater chance of flooding in any year. 

2. The area designated as a flood hazard area on a 
community’s flood hazard map, or otherwise legally 
designated. 

FLOOD HAZARD AREA SUBJECT TO HIGH 
VELOCITY- WAVE ACTION refers to area within the 
flood hazard area that is subject to high velocity wave 
action. 

FLOODWAY is the channel of the river, creek or other 
watercourse and the adjacent land areas that must be 
reserved in order to discharge the base flood without 
cumulatively increasing the water surface elevation more 
than a designated height. 

LOWEST FLOOR refers to the floor of the lowest 
enclosed area, including basement, but excluding any 
unfinished or flood-resistant enclosure, usable solely for 
vehicle parking, building access or limited storage 
provided that such enclosure is not built so as to render the 
structure in violation of this section. 

START OF CONSTRUCTION refers to the date of 
permit issuance for new construction and substantial 
improvements to existing structures, provided the actual 
start of construction, repair, reconstruction, rehabilitation, 
addition, placement or other improvement is within 180 
days after the date of issuance. The actual start of 


construction means the first placement of permanent 
construction of a building (including a manufactured 
home) on a site, such as the pouring of a slab or footings, 
installation of pilings or construction of columns. 
Permanent construction does not include land preparation 
(such as clearing, excavation, grading or filling), the 
installation of streets or walkways, excavation for a 
basement, footings, piers or foundations, the erection of 
temporary forms or the installation of accessory buildings 
such as garages or sheds not occupied as dwelling units or 
not part of the main building. For a substantial 
improvement, the actual “start of construction” means the 
first alteration of any wall, ceiling, floor or other structural 
part of a building, whether or not that alteration affects the 
external dimensions of the building. 

SUBSTANTIAL DAMAGE refers to damage to any 
origin sustained by a structure whereby the cost of 
restoring the structure to its before-damaged condition 
would equal or exceed 50 percent of the market value of 
the structure before the damage occurred. 

SUBSTANTIAL IMPROVEMENT refers to any repair, 
reconstruction, rehabilitation, addition or improvement of 
a building or structure, the cost of which equals or exceeds 
50 percent of the market value of the structure before the 
improvement or repair is started. If the structure has 
sustained substantial damage, any repairs are considered 
substantial improvement regardless of the actual repair 
work performed. The term does not, however, include 
either: 

1 . Any project for improvement of a building required to 
correct existing health, sanitary or safety code 
violations identified by the building official and that 
are the minimum necessary to assure safe living 
conditions. 

2. Any alteration of a historic structure provided that the 
alteration will not preclude the structure’s continued 
designation as a historic structure. 

211.3 Design Requirements 

2 1 1 .3. 1 Design Loads 

Structural systems of buildings or other structures shall be 
designed, constructed, connected, and anchored to resist 
flotation, collapse, and permanent lateral displacement due 
to action of flood loads associated with the design flood 
(see Section 211.3.3) and other loads in accordance with 
the load combinations of Section 203. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-240 CHAPTER 2 - Minimum Design Loads 


211.3.2 Erosion and Scour 

Tire effects of erosion and scour shall be included in the 
calculation of loads on buildings and other structures in 
flood hazard areas. 

211.3.3 Loads on Breakaway Walls 

Walls and partitions required by ASCE/SEI 24, to break 
away, including their connections to the structure, shall be 
designed for the largest of the following loads acting 
perpendicular to the plane of the wall: 

1. The wind load specified in Section 207. 

2. The earthquake load specified in Section 208. 

3. 0.48 kPa. 

The loading at which breakaway walls are intended to 
collapse shall not exceed 0.96 kPa unless the design meets 
the following conditions: 

1 . Breakaway wall collapse is designed to result from a 
flood load less than that which occurs during the base 
flood. 

2. The supporting foundation and the elevated portion of 
the building shall be designed against collapse, 
permanent lateral displacement, and other structural 
damage due to the effects of flood loads in 
combination with other loads as specified in Section 
203. 

211.4 Loads During Flooding 

211.4.1 Load Basis 

In flood hazard areas, the structural design shall be based 
on the design flood. 

211.4.2 Hydrostatic Loads 

Hydrostatic loads caused by a depth of water to the level of 
the DFE shall be applied over all surfaces involved, both 
above and below ground level, except that for surfaces 
exposed to free water, the design depth shall be increased 
by 0.30 m. Reduced uplift and lateral loads on surfaces of 
enclosed spaces below the DFE shall apply only if 
provision is made for entry and exit of floodwater. 


211.4.3 Hydrodynamic Loads 

Dynamic effects of moving water shall be determined bv 
detailed analysis utilizing basic concepts of 
mechanics. 

Exception: 

Where water velocities do not exceed 3.05 mis, dynamic 
effects of moving water shall be permitted to be 
converted into equivalent hydrostatic loads by 
increasing the DFE for design purposes by an 
equivalent surcharge depth, dh, on the headwater side . 
and above the ground level only, equal to 

. _aV 2 (211-1) 

du — — — 

2g 

where 

V = average velocity of water, m/s 
g = acceleration due to gravity, 9.81 m/s 2 

a - coefficient of drag or shape factor (not less 

than 1 .25) 

The equivalent surcharge depth shall be added to the DFE 
design depth and the resultant hydrostatic pressures applied 
to, and uniformly distributed across, the vertical projected 
area of the building or structure that is perpendicular to the 
flow. Surfaces parallel to the flow or surfaces wetted by the 
tail water shall be subject to the hydrostatic pressures for 
depths to the DFE only. 

211.4.4 Wave Loads 

Wave loads shall be determined by one of the following 
three methods: (1) by using the analytical procedures 
outlined in this section, (2) by more advanced numerical 
modeling procedures, or (3) by laboratory test procedures 
(physical modeling). 

Wave loads are those loads that result from water waves 
propagating over the water surface and striking a building 
or other structure. Design and construction of buildings and 
other structures subject to wave loads shall account for the 
following loads: waves breaking on any portion of the 
building or structure; uplift forces caused by shoaling 
waves beneath a building or structure, or portion thereof; 
wave run-up striking any portion of the building or 
structure; wave-induced drag and inertia forces; and wave- 
induced scour at the base of a building or structure, or its 
foundation. Wave loads shall be included for both V-Zones 
and A-Zones. In V-Zones, waves are 0.91 m high, or 
higher; in .coastal floodplains landward of the V-Zone, 
waves are less than 0.91 m. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 2 - Minimum Design Loads 2-241 


Nonbreaking and broken wave loads shall be calculated 
using the procedures described in Sections 211.4.2 and 
211.4.3 that show how to calculate hydrostatic and 
hydrodynamic loads. 

Breaking wave loads shall be calculated using the 
procedures described in Sections 211.4.4.1 through 
211.4.4.4. Breaking wave heights used in the procedures 
described in Sections 211.4.4.1 through 211.4.4.4 shall be 
calculated for V-Zones and Coastal A-Zones using 
Equations 211-2 and 211-3. 


211.4.4.2 Breaking Wave Loads on Vertical Walls 

Maximum pressures and net forces resulting from a 
normally incident breaking wave (depth-limited in size, 
with H b = 0.78 d s ) acting on a rigid vertical wall shall 
be calculated by the following: 

Pmax = C p Y*>d s + 1. 2y b) d s (21 1-5) 

and 

F t = 11 C pYo) d 2 s + 2. 4 Y(J) d 2 s (211-6) 


H b = 0.78 d s (211-2) where 


where 

H b = breaking wave height, m 
d s = local still water depth, m 

The local still water depth shall be calculated using 
Equation 211-3, unless more advanced procedures or 
laboratory tests permitted by this section are used. 

d s = 0.65 (BFE-G) (211-3) 


where 

G = ground elevation, m 


Ft 


Ya> 


d s 


maximum combined dynamic (C pYo) d s ) 
and static wave pressures, also 

referred to as shock pressures, kN/m 2 
net breaking wave force per unit length of 
structure, also referred to as shock, 
impulse, or wave impact force, kN/m, 
acting near the still water elevation 
dynamic pressure coefficient (1. 6 < 

C v < 3.5) (see Table 21 1-1) 
unit weight of water, kN/m3, 9.80 kN/m 3 
for fresh water and 10.05 kN/m 3 for salt 
water 

still water depth, m at base of building or 
other structure where the wave breaks 


211.4.4.1 Breaking Wave Loads on Vertical Pilings and 
Columns 

The net force resulting from a breaking wave acting on a 
rigid vertical pile or column shall be assumed to act at the 
still water elevation and shall be calculated by the 
following: 

F D = 0.5 Yb> C D DH 2 b (211-4) 

where 

F d — net wave force, kN 

= unit weight of water, in lb per cubic kN/m 3 , 

= 9.80 kN/m 3 for fresh water and 10.05 
kN/m 3 for salt water 

Yo) = unit weight of water, kN/m 3 , 9.80 kN/m 3 for 
fresh water and 10.05 kN/m 3 for salt water 

C D = coefficient of drag for breaking waves, = 
1.75 for round piles or columns, and = 2.25 
for square piles or columns 

D - pile or column diameter, m for circular 
sections, or for a square pile or column, 1.4 
times the width of the pile or column, m 

H b = breaking wave height, m 


This procedure assumes the vertical wall causes a reflected 
or standing wave against the waterward side of the wall 
with the crest of the wave at a height of 1 .2d, above the still 
water level. Thus, the dynamic static and total pressure 
distributions against the wall are as shown in Figure 211- 
1 . 

This procedure also assumes the space behind the vertical 
wall is dry, with no fluid balancing the static component of 
the wave force on the outside of the wall. If free water 
exists behind the wall, a portion of the hydrostatic 
component of the wave pressure and force disappears (see 
Figure 211-2) and the net force shall be computed by 
Equation 21 1-7 (the maximum combined wave pressure is 
still computed with Equation 21 1-5). 

Ft = I- 1 C pYo) d 2 s + 1. 9 Yo) d 2 s (211-7) 

where 

F t = net breaking wave force per unit length of 
structure, also referred to as shock, impulse, 
or wave impact force, kN/m, acting near the 
still water elevation 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


2-242 CHAPTER 2 - Minimum Design Loads 


C p = dynamic pressure coefficient (1. 6 < C p < 
3.5) (see Table 21 1-1) 

, = unit weight of water, kN/m 3 , = 9.80 kN/m 3 

for fresh water and 10.05 kN/m 3 for salt 
water 

d s = still water depth, m at base of building or 
other structure where the wave breaks 

211.4.4.3 Breaking Wave Loads on Non-vertical 
Walls 

Breaking wave forces given by Equations 21 1-6 and 21 1-7 
shall be modified in instances where the walls or surfaces 
upon which the breaking waves act are non-vertical. The 
horizontal component of breaking wave force shall be 


given by 

F nv = F t sin 2 a (211-8) 

where 

Fnv 

horizontal component of breaking wave 
force, kN/m 

F t 

net breaking wave force acting on a vertical 
surface, kN/m 

a = 

vertical angle between non-vertical surface 
and the horizontal 

211..4.4.4 

Breaking Wave Loads from Obliquely 
Incident Waves 


Breaking wave forces given by Equations 211-6 and 211-7 
shall be modified in instances where waves are obliquely 
incident. Breaking wave forces from non-normally 
incident waves shall be given by 

F oi = F t sin 2 a (211-9) 

where 

F oi = horizontal component of obliquely incident 
breaking wave force, kN/m 

a = net breaking wave force (normally incident 
waves) acting on a vertical surface, kN/m 

211.4.5 Impact Loads 

Impact loads are those that result from debris, ice, and any 
object transported by floodwaters striking against buildings 
and structures, or parts thereof Impact loads shall be 
determined using a rational approach as concentrated loads 
acting horizontally at the most critical location at or below 
the DFE. 


211.5 Establishment of Flood Hazard Areas 

To establish flood hazard areas, the governing body shall 
adopt a flood hazard map and supporting data. The flood 
hazard map shall include, at a minimum, areas of special 
flood hazard where records are available. 

211.6 Design and Construction 

The design and construction of buildings and structures 
located in flood hazard areas, including flood hazard areas 
subject to high velocity wave action. 

211.7 Flood Hazard Documentation 

The following documentation shall be prepared and sealed 
by an engineer-of-record and submitted to the building 
official: 

1. For construction in flood hazard areas not subject to 

high-velocity wave action: 

1.1 The elevation of the lowest floor, including the 
basement, as required by the lowest floor 
elevation. 

1.2 For fully enclosed areas below the design flood 
elevation where provisions to allow for the 
automatic entry and exit of floodwaters do not 
meet the minimum requirements, construction 
documents shall include a statement that the 
design will provide for equalization of hydrostatic 
flood forces. 

1.3 For dry flood-proofed nonresidential buildings, 
construction documents shall include a statement 
that the dry flood-proofing is designed. 

2. For construction in flood hazard areas subject to high- 

velocity wave action: 

2.1 The elevation of the bottom of the lowest 
horizontal structural member as required by the 
lowest floor elevation. 

2.2 Construction documents shall include a statement 
that the building is designed, including that the 
pile or column foundation and building or 
structure to be attached thereto is designed to be 
anchored to resist flotation, collapse and lateral 
movement due to the effects of wind and flood 
loads acting simultaneously on all building 
components, and other load requirements of 
Section 203. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 2 - Minimum Design Loads 2-243 


2.3 For breakaway walls designed to resist a nominal 
load of less than 0.5 kPa or more than 1.0 kPa, 
construction documents shall include a statement 
that the breakaway wall is designed. 


Table 211-1 Value of Dynamic Pressure Coefficient, C p 


Building Category 

C p 

I 

1.6 

II 

2.8 

II 

3.2 

IV 

3.5 


ASCE/SEI 

American Society of Civil Engineers 
Structural Engineering Institute 
1801 Alexander Bell Drive 
Reston, VA 20191-4400 

ASCE/SEI 24 

Section 5.3.3 

Flood Resistant Design and Construction , 1998 


211.8 Consensus Standards and Other Referenced 
Documents 

This section lists the consensus standards and other 
documents which are adopted by reference within this 
chapter: 


Vertical Wall 



Figure 211-1 

Normally Incident Breaking Wave Pressures Against a Vertical Wall 
(Space Behind Vertical Wall Is Dry) 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


-244 CHAPTER 2 - Minimum Design Loads 



(Still Water Level Equal on Both Sides of Wall) 


n 





Association of Structural Engineers of the Philippines, Inc. (ASEP) 


NSCP Cl 01 -15 


Chapter 3 

EARTHWORKS AND 
FOUNDATIONS 


NATIONAL STRUCTURAL CODE OF THE PHILIPPINES 
VOLUME I 

BUILDINGS, TOWERS AND 
OTHER VERTICAL STRUCTURES 

SEVEHTH EDITION, 2015 


Association of Structural Engineers of the Philippines, Inc. 

Suite 713, Future Point Plaza Condominium 1 
112 Panay Avenue, Quezon City, Philippines 1100 

Tel. No. : (+632) 410-0483 
Fax No. : (+632) 411-8606 
Email: aseponline@gmail.com 
Website: http://www.aseponline.org 



National Structural Code of the Philippines Volume I, 7th Edition, 2015 


CHAPTER 3 - Earthworks and Foundations 3-1 


Table of Contents 


SECTION 301 - GENERAL REQUIREMENTS 

301.1 Scope 

301 .2 Quality and Design 

301.3 Allowable Bearing Pressures 

301.4 Definitions 

SECTION 302 - EXCAVATION AND FILLS 

302.1 General 

302.2 Cuts 

302.4 Fills * 

302.5 Setbacks 

302.6 Drainage and Terracing 

302.7 Erosion Control 

SECTION 303 - FOUNDATION INVESTIGATION 

303.1 General 

303.2 Soil Classification _ 

303.3 Questionable Soils 

303.4 Liquefaction Study 

303.5 Expansive Soils 

303.6 Compressible Soils...,* 

303.7 Reports 

303.8 Soil Tests 

303.9 Liquefaction Potential and Soil Strength Loss .. 

303.10 Adj acent Loads 

303.1 1 Drainage 

303.12 Plate Load Test 


,3-3 


,.3-3 


3-3 

3-3 

.. ,3-3 


,3-3 


.....3-3 

.....3-5 


...3-6 




.3-7 


3-8 


...3-8 


..3-9 


3-9 


3-9 


..,.*,3-9 

...3-10 

...3-10 

...3-10 

...3-12 

....3-12 

...3-12 


SECTION 304 - ALLOWABLE FOUNDATION AND LATERAL PRESSURES . 

304.1 From Geotechnical Site Investigation and Assessment 

304.2 Presumptive Load-Bearing and Lateral Resisting Values "T" 

304.3 Minimum Allowable Pressures 

304.4 Foundations Adjacent to Existing Retaining/Basement Walls 

SECTION 305 - FOOTINGS 

305.1 General 

305.2 Footing Design 

305.4 Stepped Foundations 

305.5 Footings on or Adjacent to Slopes.... 

305.6 Foundation Plates or Sills 

305.7 Designs Employing Lateral Bearing __ 

305.8 Grillage Footings 

305.9 Bleacher Footings _ 


3-12 

V...342 

3-13 

3-13 

....3-13 


3-14 



National Structural Code of the Philippines Volume I, 7th Edition, 2015 


3-2 CHAPTER 3 - Earthworks and Foundations 


SECTION 306 - PILES-GENERAL REQUIREMENTS 3-17 

30&. 1 General - **■- * — ■ 3-17 

306.2 Interconnection * * * 3-17 

306.3 Determination of Allowable Loads * £ - * ** 3-17 

306.4 Static Load Test '•>. - »-*. — — 3-18 

306.5 Dynamic Load Test . .... ■«« - * * 3-18 

306.6 Column Action * .......... ... - - * * 3-18 

306.7 Group Action * * * * * — - 3-18 

306.8 Lateral Loads — * - *»■ ■«** 3-18 

306.9 Piles in Subsiding Areas - — •«* *■— * wvr. 3-19 

306.10 Water Jetting * "■—* 3-19 

306.10 Protection of Pile Materials .. ....... . — - * * •••.• 3-19 

306.12 Allowable Loads * * * ■«* 3-19 

306.13 Use of Higher Allowable Pile Stresses - * * 3-19 

SECTION 307 - PILES-SPECIFIC REQUIREMENTS 3-20 

307.1 Round Wood Piles - * * 3-20 

307.2 Uncased Cast-In-Place Concrete Piles ............. — - * ■ 3-20 

307.3 Metal-Cased Concrete Piles . * — — * — 3-20 

307.4 Precast Concrete Piles - — - 3-21 

307.5 Precast Prestressed Concrete Piles (Pretensioned) . * * 3-21 

307.6 Structural Steel Piles....... ♦ — - 3-22 

307.7 Concrete-Filled Steel Pipe Piles >*♦— . *-■**«-—** 3-22 

SECTION 308 - FOUNDATION CONSTRUCTION-SEISMIC ZONE 4 3-23 

308.1 General . *■■■■ ---- 3-23 

308.2 Foundation and Geotechnical Investigations 3-23 

308.3 Footing Foundations **■*■**•■■— 3-23 

308.4 Pier and Pile Foundations * - — * * 3-23 

308.5 Driven Pile Foundations — — 3-24 

308.6 Cast-In-Place Concrete Foundations 3-26 

SECTION 309 - SPECIAL FOUNDATION, SLOPE STABILIZATION AND MATERIALS OF 
CONSTRUCTION 26 

309.1 Special Foundation Systems 3-26 

309.2 Acceptance and Approval 3-26 

309.3 Specific Applications - *■— - »*■■* 3-26 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-3 


SECTION 301 

GENERAL REQUIREMENTS 

301.1 Scope 

This chapter sets forth requirements for excavations, fills, 
footings and foundations for any building or structure. 

301.2 Quality and Design 

The quality and design of materials used structurally in 
excavations, fills, footings and foundations shall conform to 
the requirements specified in Chapters 4, 5, 6 and 7. 

301.3 Allowable Bearing Pressures 

Allowable stresses and design formulas provided in this 
chapter shall be used with the allowable stress design load 
combinations specified in Section 203.4. 

301.4 Definitions 

See Sections 102 and 202. 


SECTION 302 

EXCAVATIONS AND FILLS 

302.1 General 

Excavation or fills for buildings or structures shall be 
constructed or protected such that they do not endanger life 
or property. Reference is made to Section 109 of this code 
for requirements governing excavation, grading and 
earthwork construction, including fills and embankments. 

302.2 Cuts 

302.2.1 General 

Unless otherwise recommended in the approved 
geotechnical engineering report or engineering report, cuts 
shall conform to the provisions of this section. In the 
absence of an approved geotechnical engineering report, 
these provisions may be waived for cuts 3 m or less in 
height, involving intact rock or hard soil, that are not 
intended to support structures. 

302.2.2 Slopes 

The slope of cut surfaces shall be no steeper than is safe for 
the intended use and shall be no steeper than 1 unit vertical 
in 2 units horizontal (50% slope) unless a geotechnical 
engineering report, stating that the site has been 
investigated, and giving an opinion that a cut at a steeper 
slope shall be stable and not create a hazard to public or 
private property, is submitted and approved. Such cuts shall 
be protected against erosion or degradation by sufficient 
cover, drainage, engineering and/or biotechnical means. 

302.3 Excavations 

302.3.1 Footings 

Existing footings or foundations which may be undermined 
by any excavation shall be underpinned adequately or 
otherwise protected against settlement and shall be 
protected against lateral movement. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


3-4 CHAPTER 3 - Earthworks and Foundations 


302.3.2 Protection of Adjoining Property 


302.3.3 Support of Excavations and Open Cuts 


y The following provisions shall apply unless prevailing local Excavations or open cuts in excess of 1.5m in depth shall 


laws are deemed more stringent from an engineering have adequately designed shoring or support to protect 


against collapse. 


standpoint: 


1 . Before commencing the excavation, the person making 
or causing the excavation to be made shall notify in 
writing the owners of adjoining building not less than 
10 days before such excavation is to be made and that 
the adjoining building shall be protected. The condition 
of the adjoining building shall be documented to 
include photographs prior to excavation. Technical 
documents pertaining to the proposed underpinning 
and excavation plan shall be provided the owner of the 
adjacent property. 


FOR: X ■ 2 for properly compacted 1111a 


FOR: a) H * 20.0m: 


X ml0 ■ 1 for cuts on hard soil and 
Intact rock 


W, a 2.0 m: 
h, s 10.0m: 


| Permit Area Boundary 


X mln - for loose or uncompacted soils, 
a thorough soil Investigation to 
be conducted by a certified 
Geotechnical Engineer Is required 


b) H * 20.0m: 



W, 2 4.0 m: 
h, s 10.0m: 


1 0.6m 
Imln. 





| Natural or Fi nish Grade 


X/" 


Properly designed Interceptor 
drains with outfalls spaced at 
regular Intervals 


F0R: a) H = height of slope 


b) w i ■ width of terrace 


Figure 302-1 Cut Slopes 


2. Unless it can be shown through a detailed geotechnical 
investigation that underpinning is unnecessary, any 
person making or causing an excavation shall protect 
the excavation so that the soil of adjoining property 
will not cave in or settle. 

In cases where the adjacent existing structure will have 
more basements than the proposed building, the foundation 
of the proposed building should be designed so as not to 
impart additional lateral earth pressures on the existing 
building (see Section 304.4). 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-5 


302.4 Fills 
^302.4.1 General 

Unless otherwise recommended in the approved 
geotechnical engineering report, fills shall conform to the 
provisions of this section. In the absence of an approved 
geotechnical engineering report or engineering report, these 
provisions may be waived for minor fills (H < 2.0 m) not 
intended to support structures. 

Fills to be used to support the foundations of any building 
or structure shall be placed in accordance with accepted 
engineering practice. A geotechnical investigation report 
and a report of satisfactory placement of fill, both 
acceptable to the building official, shall be submitted when 
required by the building official 

No fill or other surcharge loads shall be placed adjacent to 
any building or structure unless such building or structure is 
capable of withstanding the additional vertical and 
horizontal loads caused by the fill or surcharge. 

Fill slopes shall not be constructed on natural slopes steeper 
than 1 unit vertical in 2 units horizontal (50% slope). 

302.4.2 Preparation of Ground 

The existing ground surface shall be adequately prepared to 
receive fill by removing any deleterious materials, 
non-complying fill, topsoil and other unsuitable materials, 
and by scarifying to provide a bond with the new fill. 

Where the natural slopes are steeper than 1 unit vertical in 
5 units horizontal (20% slope) and the height is greater than 
1.5 m, the ground surface shall be prepared by benching 
into sound bedrock or other competent material as 
determined by the geotechnical engineer. The bench under 
the toe of a fill on a slope steeper than 1 unit vertical in 
5 units horizontal (20% slope) shall be at least 3 m wide. 

The area beyond the toe of fill shall be sloped to drain or a 
paved drain shall be provided. When fill is to be placed 
over a cut, the bench under the toe of fill shall be at least 
3 m wide but the cut shall be made before placing the fill 
and acceptance by the geotechnical engineer as a suitable 
foundation for fill. 


302.4.3 Fill Material 

Any organic or deleterious material shall be removed and 
will not be permitted in fills. Except as permitted by the 
geotechnical engineer, no rock or similar irreducible 
material with a maximum dimension greater than 200 mm 
shall be buried or placed in fills. 

Exception: 

The placement of larger rock may be permitted when the 
geotechnical engineer properly devises a method of 
placement, and continuously inspects its placement and 
approves the fill stability . The following conditions shall 
also apply: 

1 . Prior to issuance of the grading permit, potential rock 
disposal areas shall be delineated on the grading plan . 

2. Rock sizes greater than 300 mm in maximum 
dimension shall be 3 m or more below grade, measured 
vertically. 

3. Rocks shall be placed so as to assure filling of all voids 
with well-graded soil. 

302.4.4 Compaction 

All fills shall be compacted in litis not exceeding 20 cm in 
thickness to a minimum of 90 percent of maximum density 
as determined by ASTM Standard D-1557. In-place density 
shall be determined in accordance with ASTM D-1556, 
D-2167, D-2922, D-3017 or equivalent. For clean granular 
materials, the use of the foregoing procedures is 
inappropriate. Relative density criteria shall be used based 
on ASTM D5030-04. A minimum of three tests for every 
500 m 2 area should be performed for every lift to verify 
compliance with compaction requirements. 

302.4.5 Slope 

The slope of fill surfaces shall be no steeper than is safe for 
the intended use. Fill slopes shall be no steeper than 1 unit 
vertical in 2 units horizontal (50% slope) unless 
substantiating data justifying steeper slopes are submitted 
and approved. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 



3-6 CHAPTER 3 - Earthworks and Foundations 


302.5 Setbacks 

302.5.1 General 

Cut and fill slopes shall be set back from site boundaries in 
accordance with this section subject to verification with 
detailed slope stability study. Setback dimensions shall be 
horizontal distances measured perpendicular to the site 
boundary. Setback dimensions shall be as shown in 
Figure 302-1. 

302.5.2 Top of Cut Slope 

The top of cut slopes shall not be made nearer to a site 
boundary line than one fifth of the vertical height of cut 
with a minimum of 0.6 m and a maximum of 3 m. The 
setback may need to be increased for any required 
interceptor drains. 

302.5.3 Toe of Fill Slope 

The toe of a fill slope shall be made not nearer to the site 
boundary line than one half the height of the slope with a 
minimum of 0.6 m and a maximum of 6 m. Where a fill 
slope is to be located near the site boundary and the 
adjacent off-site property is developed, special precautions 
shall be incorporated in the work as the building official 
deems necessary to protect the adjoining property from 
damage as a result of such grading. These precautions may 
include but are not limited to: 

1. Additional setbacks. 

2. Provision for retaining or slough walls. 

3. Mechanical stabilization or chemical treatment of the 
fill slope surface to minimize erosion. 

4. Rockfall protection 

5. Provisions for the control of surface subsurface waters. 

302.5.4 Modification of Slope Location 

The building official may approve alternate setbacks. The 
building official may require an investigation and 
recommendation by a qualified geotechnical engineer to 
demonstrate that the intent of this section has been satisfied. 

302.6 Drainage and Terracing 

302.6.1 General 

Unless otherwise indicated on the approved grading plan, 
drainage facilities and terracing shall conform to the 
provisions of this section for cut or fill slopes steeper than 
1 unit vertical in 3 units horizontal (33.3% slope). 


302.6.2 Terraces 

Terraces at least 2.0m in width shall be established at not 
more than 10.0m vertical intervals on all cut or fill slopes to 
control surface drainage and debris except that where only 
one terrace is required, it shall be at mid-height. For cut or 
fill slopes greater than 20.0m in vertical height, terraces at 
least 4.0m in width shall be established at not more than 
10.0m vertical intervals. Terrace widths and vertical 
spacing for cut and fill slopes greater than 40.0m in height 
shall be designed by the Geotechnical Engineer and 
approved by the Building Official. Suitable access shall be 
provided to permit proper cleaning and maintenance. 

Swales or ditches on terraces shall be designed to 
effectively collect surface water and discharge to an outfall. 
It shall have a minimum gradient of 0.5 percent and must be 
paved with reinforced concrete not less than 75 mm in 
thickness or an approved equal paving material. 

A single run of swale or ditch shall not collect runoff from a 
tributary area exceeding 1,000 m 2 (projected area) without 
discharging into a down drain. 

302.6.3 Subsurface Drainage 

Cut and fill slopes shall be provided with surface drainage 
as necessary for stability. 

302.6.4 Disposal 

All drainage facilities shall be designed to carry waters to 
the nearest practicable drainage way approved by the 
Building Official or other appropriate jurisdiction as a safe 
place to deposit such waters. Erosion of ground in the area 
of discharge shall be prevented by installation of non- 
erosive down drains or other devices or splash blocks. 

Building pads shall have a drainage gradient of 2 percent 
toward approved drainage facilities, unless waived by the 
Building Official. 

Note: 

The gradient from the building pad may be 1 percent if all 
of the following conditions exist throughout the permit 
area: 

L No proposed fills are greater than 3 m in maximum 
depth . 

2. No proposed finish cut or fill slope faces have a 
vertical height in excess of 3 m. 

3. No existing slope faces steeper than 1 unit vertical in 
10 units horizontal (10% slope) have a vertical height 
in excess of 3m. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-7 


302.6.5 Interceptor Drains 

Paved or Lined interceptor drains shall be installed along 
the top of all cut slopes where the tributary drainage area 
above slopes toward the cut has a drainage path greater than 
12 m measured horizontally. Unless specified otherwise by 
the Engineer of Record, interceptor drains shall be paved 
with a minimum of 75 mm of concrete or gunite and 
reinforced. They shall have a minimum depth of 300 mm 
and a minimum paved width of 750 mm measured 
horizontally across the drain. The slope of drain shall be 
approved by the building official. Interceptor drains shall be 
provided with outfalls spaced at regular intervals sufficient 
enough to avoid overflow of drains. In cases where neither 
reinforced concrete nor reinforced gunite shall be used as 
the paving material for the drain, sufficient testing on the 
alternative material must be conducted to determine its 
effectiveness and durability as a channel lining material. 

302.7 Erosion Control 

302.7.1 Slopes 

The faces of cut and fill slopes shall be prepared and 
maintained to control against erosion. This erosion control 
may consist of biotechnical or geosynthetic intervention 
adapted to the local conditions. The protection for the 
slopes shall be installed as soon as practicable and prior to 
calling for final approval. Where cut slopes are not subject 
to erosion due to the erosion-resistant character of the 
materials, such protection may be omitted. 

302.7.2 Other Devices 

Where necessary, check dams, cribbing, riprap or other 
devices or methods shall be employed to control erosion 
and provide safety. 


and biological attack, mechanical damage, creep, 
installation damage and pH conditions to the reinforcement. 

Select Granular Backfill shall consist of sound, durable, 
granular material free from organic matter or other 
deleterious material (such as shale or other soft particles 
with poor durability). 

The select granular backfill materials for these earth 
structures shall conform to Grading Requirements as stated 
in Table 302.1 


Table 302-1 Grading Requirements 


Standard Sieve 

Percent by Mass Passing 

Opening (mm) 

Designated Sieve 


(AASHTO T 27 and Til) 

100 

100 

0.0425 

0-60 

0.075 

0-15 


The angle of internal friction for the backfill material shall 
not be less than 34°. 

The assigned cohesion value during the design stage for the 
backfill material within the reinforced zone shall not exceed 
5 kPa. 

The soils should be compacted to no less than 95% MDD 
determine according to AASHTO T 99 Method C or D and 
corrected for oversized material according to AASHTO T 
99, Note 9. 

The material shall have a Plasticity Index of not more than 
15 for rigid faced MSE structures, and not more than 20 for 
flexible or ductile faced MSE structures, as determined by 
AASHTO T 90. 


302.7.2 Scour Protection 

Retaining structures and foundations located on stream 
banks and beds shall be provided with appropriate 
countermeasures, designed on the basis of a detailed 
engineering study, for long-term protection against scouring 
and erosion. 

302.8 MSE Structures and Similar Reinforced 
Embankments and Fills 

The design of Mechanically Stabilized Earth (MSE) 
Structures and Similar Reinforced Embankments and Fills 
shall incorporate provisions for internal and external 
drainage. 

The design for the required reinforcement shall take into 
consideration the detrimental effects of corrosion, chemical 


Electrochemical requirements for Mechanically Stabilized 
Earth (MSE) retaining walls with metallic reinforcements 
shall comply with summarized in Table 302-2. 


Table 302-2 Electrochemical Requirements 


Test 

Requirements 

Resistivity, AASHTO 

T 288 

pH, AASHTO T 289 
Sulfate Content 
AASHTO T 290 
Chloride Content 
AASHTO T 291 

3000 Q-cm min. 

5.0 to 10.0 

200 ppm max. 

1 00 ppm max. 


Electrochemical requirements for Mechanically Stabilized 
Earth MSE retaining walls with Geosynthetic 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


3-8 CHAPTER 3 - Earthworks and Foundations 


reinforcements specify that the pH shall be between 5.0 to 
10.0 as determined by AASHTO T 289. 


SECTION 303 

FOUNDATION INVESTIGATION 

303.1 General 

Foundation investigation shall be conducted and a 
Professional Report shall be submitted at each building site 
For structures two storeys or higher, an exhaustive 
geotechnical study shall be performed to evaluate in-situ 
soil parameters for foundation design and analysis. The 
minimum required number of boreholes per structure based 
on footprint area is summarized in Table 303-1. All of these 
boreholes should fall within the footprint of the structure, 
and should generally be uniformly distributed throughout 
the building footprint. Unless specified by the consulting 
Geotechnical Engineer, all boreholes should be drilled to a 
depth of at least five meters into hard strata or until a 
suitable bearing layer is reached. For buildings with 
basements, the depth of boring should extend to twice the 
least dimension of the structure’s footprint (2B) added to 
the depth of the basement. 

Table 303-1 Minimum required number of boreholes per 
structure. 


FOOTPRINT AREA OF 
STRUCTURE (m 2 ) 

MINIMUM REQUIRED 
NUMBER OF 
BOREHOLES* 

A < 50 

1 

50 < A < 500 

2 

A >500 

2 + (A/1000)** 


(Rounded Up to Nearest 
Integer) 


*The minimum required number of boreholes should in no 
way be construed as an upper limit value. 

** “A” corresponds to the footprint area of the structure in 

2 

m . 

An exhaustive geotechnical investigation should also be 
conducted in cases of: 

1) questionable soils, expansive soils, or problematic 
soils (e.g. liquefiable, organic, compressible, 
sensitive, etc.); 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 3 - Earthworks and Foundations 3-9 


2) to determine whether the existing groundwater 
table is above or within 1.5 meters below the 
elevation of the lowest floor level; 

3) where such floor is located below the finished 
ground level adjacent to the foundation; 

4) in cases where the use of pile foundations and/or 
ground improvement are anticipated; 

5) in areas underlain by rock strata where the rock is 
suspected to be of questionable characteristics or 
indicate variations in the structure of the rock or 
where solution cavities or voids are expected to be 
present in the rock; and 

6) other cases deemed necessary by the Geotechnical 
Engineer. 

The Building Official may require that the interpretation 
and evaluation of the results of the foundation investigation 
be made by a geotechnical engineer, 

303.2 Soil Classification 

For the purposes of this chapter, the definition and 
classification of soil materials for use in Table 304-1 shall 
be according to ASTM D-2487. 

Soil classification shall be based on observation and any 
necessary tests of the materials disclosed by borings or 
excavations made in appropriate locations. Additional 
studies may be necessary to evaluate soil strength, the effect 
of moisture variation on soil-bearing capacity, 
compressibility, liquefaction susceptibility and expansion 
potential. 

303.3 Questionable Soils 

Where the classification, strength or compressibility of the 
soil are unknown, or where a load bearing value superior to 
that specified in this code is claimed, the Building Official 
shall require that these be verified through the necessary 
geotechnical study stipulated in Section 303.1. 

303.4 Liquefaction Study 

A liquefaction susceptibility assessment in accordance with 
accepted practice is warranted if both conditions below are 
discovered during the course of the geotechnical 
investigation: 

1 . Shallow ground water, 2 m or less. 

2, Unconsolidated saturated sandy alluvium (N < 15) 


Exception: 

The building official may waive this evaluation upon receipt 
of written opinion of a qualified geotechnical engineer that 
liquefaction is not probable. 

303.5 Expansive Soils 

Soils meeting all four of the following provisions shall be 
considered expansive: 

1. Plasticity index (PT) of 15 or greater, determined in 
accordance with ASTM D 4318. 

2. More than 10 percent of the soil particles pass a No. 
200 sieve (75 m), determined in accordance with 
ASTMD-422. 

3. More than 10 percent of the soil particles are less than 
5 micrometers in size, determined in accordance with 
ASTM D-422. 

4. Expansion index greater than 20, determined in 
accordance with ASTM D-4829. 

Tests that show compliance with Items 1, 2 and 3 shall not 
be required if the test prescribed in Item 4 is conducted. 

303.5.1 Design for Expansive Soils 

Footings or foundations for buildings and structures 
founded on expansive soils shall be designed in accordance 
with Section 1805,8.1 or 1805.8.2. 

Footing or foundation design need not comply with Section 
303.5.3 or 303.5.4 where the soil is removed in accordance 
with Section 303.5.4, nor where the building official 
approves stabilization of the soil in accordance with Section 
303.5.5. 

303.5.2 Foundations 

Footings or foundations placed on or within the active zone 
of expansive soils shall be designed to resist differential 
volume changes and to prevent structural damage to the 
supported structure. Deflection and racking of the supported 
shall be limited to that which will not interfere with the 
usability and serviceability of the structure. 

Foundations placed below where volume change occurs or 
below expansive soil shall comply with the following 
provisions: 

1. Foundations extending into or penetrating expansive 
soils shall be designed to prevent uplift of the 
supported structure. 

2. Foundations penetrating expansive soils shall be 
designed to resist forces exerted on the foundation due 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


3-10 CHAPTER 3 - Earthworks and Foundations 


to soil volume changes or shall be isolated from the 
expansive soil. 

303.5.3 Slab-on-Ground, Foundations 

Moments, shears and deflections for use in designing slab- 
on-ground, mat or raft foundations on expansive soils shall 
be determined in accordance with WR1/CRSI Design of 
Slab-on-Ground Foundations or PTI Standard 
Requirements for Analysis of Shallow Concrete 
Foundations on Expansive Soils. Using the moments, 
shears and deflections determined above, non-prestressed 
slabs-on-ground, mat or raft foundations on expansive soils 
shall be designed in accordance with PTI Standard 
Requirements for Design of Shallow Post-Tensioned 
Concrete Foundations on Expansive Soils. It shall be 
permitted to analyze and design such slabs by other 
methods that account for soil -structure interaction, the 
deformed shape of the soil support, the place or stiffened 
plate action of the slab as well as both center lift and edge 
lift conditions. Such alternative methods shall be rational 
and the basis for all aspects and parameters of the method 
shall be available for peer review. 

303.5.4 Removal of Expansive Soils 

Where expansive soil is removed in lieu of designing 
footings or foundations in accordance with Section 302.3.2, 
the soil shall be removed to a depth sufficient to ensure a 
constant moisture content in the remaining soil. 
Fill material shall not contain expansive soils and shall 
comply with Section 302.3.3. 

Exception: 

Expansive soil need not be removed to the depth of constant 
moisture, provided the confining pressure in the expansive 
soil created by the fill and supported structure exceeds the 
swell pressure provided that the confining pressure 
resulting from the fill and structural dead loads exceed the 
swell pressure by 20%. 

303.5.5 Stabilization 

Where the active zone of expansive soils is stabilized in lieu 
of designing footings or foundations in accordance with 
Section 306.2, the soil shall be stabilized by chemical, 
dewatering, pre-saturation or equivalent established 
techniques. 

303.6 Compressible Soils 

If the borehole data show that the proposed structures are to 
be built above compressible fine-grained soils (with N< 6 ), 
it is recommended that consolidation tests be performed in 
accordance with ASTM D 2435 to determine the settlement 
parameters for the site. 


If wide, massive loads within the structures to be built on 
compressible fine-grained soils are to be expected for 
prolonged periods of time, the settlement effects on existing 
adjacent structures should be evaluated as well. 

303.7 Reports 

The soil classification and design-bearing capacity shall be 
shown on the plans, unless the foundation conforms to 
Table 305-1. The building official may require submission 
of a written report of the investigation, which shall include, 
but need not be limited to, the following information: 

1 . A plot showing the location of all test borings, 
surroundings and/or in-situ tests and excavations. 

2. Technical descriptions and classifications of the 
materials encountered. 

3. Elevation of the water table, if encountered. 

4. Recommendations for foundation type and design 
criteria, including bearing capacity, provisions to 
mitigate the effects of differential settlements and 
expansive soils, provisions to mitigate the effects of 
liquefaction and soil strength loss, provisions for 
special foundation solutions, provisions for ground 
improvement measures, and effects of loads on and due 
to adjacent structures. 

5. Expected total and differential settlement. 

6. Laboratory test results of soil samples. 

7. Field borehole log containing the following 
information 

a. Project location 

b. Depth of borehole 

c. Ground elevation 

d. Ground water table elevation 

e. Date started and finished 

The soil classification and design-bearing capacity shall be 
shown on the plans, unless the foundation conforms to 
Table 305-1. 

When expansive soils are present, the Building Official 
may require that special provisions be made in the 
foundation design and construction to safeguard against 
damage due to this expansiveness. The building official 
may require a special investigation and report to provide 
these design and construction criteria. 

303.8 Soil Tests 

Tables 303-2 and 303-3 summarize the commonly used 
field and laboratory tests needed in determining the in-situ 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-1 1 


soil parameters for use in foundation design and analysis. 


Table 303-3 Geophysical Tests 


Table 303-2 Laboratory and Field Tests 


Laboratory / 
Field Test 

ASTM/ Test 
Designation 

Output Data / 
Parameter 
Obtained 

Classification of Soils 

Moisture content 

D22 16-05 

Moisture/ water 
content 

Grain size 
analysis 

D422-63 

Soil gradation 

Atterberg Limits 

D43 18-05 

Liquid limit, 
plastic limit 

uses 

D2487-00 

Classification of 
soils 

Specific Gravity 

D854-05 

Specific gravity 

Shrinkage Limit 

D427-04 

Shrinkage limit 

Organic Matter 

D2974-00 

Moisture content, 
ash content and 
percent organic 
matter in soil 

Swedish Weight 

Sounding Test 

jis 

A1221:2002 

N sw - value 
indicating, 
undrained soil shear 
strength 

UCT Test (Soils) 

D2 166-00 

Strength 

parameters 

Tri-axial (UU 
Test) 

D2850-03a 

Strength 

parameters 

Tri-axial (CU 

Test) 

D4767-04 

Strength 

parameters 

Oedometer (1-D 
Consolidation) 

D2435-04 

Consolidation 

parameters 

Laboratory Vane 
Shear 

D4648-05 

Strength 

parameters 

Direct Shear 

Test 

D3080-04 

Strength 

parameters 

UCT for Intact 
Rock 

D2938-95 

Strength 

parameters 

Standard 

Penetration Test 

D1586-99 

N- value 

Modified Proctor 
Test 

D1557-02 

Maximum dry 
density 

Standard Proctor 

Test 

D698-00a 

Maximum dry 
density 

Field Density 

Test 

D1556-00 

Maximum dry 
density 

CBR Lab Test 

D1883-05 

CBR 

Cone Penetration 
Test 

D3441-05 

Soil strength 
parameters 


Field Test 

ASTM 

Designation 

Output Data / 
Parameter 
Obtained 

Geophysical Tests 

Seismic 

refraction 

D 5777-00 

Maps subsurface 
geologic conditions, 
lithologic units and 
fractures. 

Seismic 

refraction 

D 7128 

Map the top of 
bedrock. Estimate 
elastic wave velocity 
of subsurface 
materials. 

Ground 

Penetrating 

Radar (GPR) 

D 6432-11 

Maps lateral 
continuity of 
lithologic units and 
detects changes in 
the acoustic 
properties of 
subsurface 
geomaterials. 

Crosshole 
seismic survey 

D 4428 

p-wave and s-wave 
velocity 

determination, elastic 
moduli determination 

Downhole 
seismic survey 

D 7400 

p-wave and s-wave 
velocity 
determination, 
elastic moduli 
determination 

Geo-resistivity 

Survey 

D 6431-99 

Determine 
horizontal traveling 
compression and 
shear seismic 
waves at test sites. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


3-12 CHAPTER 3 - Earthworks and Foundations 


303.9 Liquefaction Potential and Soil Strength Loss 

When required by Section 303.3, the potential for soil 
liquefaction and soil strength loss during earthquakes shall 
be evaluated during the geotechnical investigation. The 
geotechnical evaluation shall assess potential consequences 
of any liquefaction and soil strength loss, including 
estimation of differential settlement, lateral movement or 
reduction in foundation soil-bearing capacity, and discuss 
mitigating measures. Such measures shall be given 
consideration in the design of the building and may include, 
but are not limited to: ground stabilization, selection of 
appropriate foundation type and depths, selection of 
appropriate structural systems to accommodate anticipated 
displacements, or any combination of these measures. 

The potential for liquefaction and soil strength loss shall be 
evaluated for a site peak ground acceleration that, as a 
minimum, conforms to the probability of exceedance 
specified in Section 208.6.2. Peak ground acceleration may 
be determined based on a site-specific study taking into 
account soil amplification effects. 

In the absence of such a study, peak ground acceleration 
may be assumed equal to the seismic zone factor in' 
Table 208-3. 

303.10 Adjacent Loads 

Where footings are placed at varying elevations, the effect 
of adjacent loads shall be included in the foundation design. 

303.11 Drainage 

Provisions shall be made for the control and drainage of 
surface water around buildings. (See also Section 305.5.5.) 
and ensure that scour will not threaten such structures. 

303.12 Plate Load Test 

The plate load test is generally used for determination of 
soil subgrade properties for rigid foundations. If used for 
building foundations, it must be emphasized that the Depth 
of Influence is only up to twice (2B) the width (B) of the 
test plate. Care must be used when extending the results to 
deeper depths as well as layered soils and variable 
subsurface conditions. 


SECTION 304 

ALLOWABLE FOUNDATION AND 
LATERAL PRESSURES 

304.1 From Geotechnical Site Investigation and 
Assessment 

The recommended allowable foundation and lateral 
pressures shall be estimated from a reasonably exhaustive 
geotechnical site investigation and assessment, which shall 
include at least the following: 

a. Description of regional geologic characteristics; 

b. Characterization of in-situ geotechnical conditions; 

c. Factual report on the in-situ and laboratory tests 
performed to characterize the site (See Section 303,7 
for a list of in-situ and laboratory tests commonly 
carried out for geotechnical site characterization); 

d. Disclosure of the assumptions and the applicable 
analytical or empirical models used in estimating the 
allowable foundation and lateral pressures; 

e. Calculations carried out and Factor of Safety (FS) 
assumed in arriving at the recommended allowable 
foundation and lateral pressures; and 

f. Evaluation of existing potential geologic hazards and 
those that may be induced or triggered by the 
construction/installation of the structure. 

The geotechnical site investigation and assessment shall be 
performed by a geotechnical engineer. 

A geotechnical investigation and assessment shall be 
presented in a report. The report, together with a brief 
resume and a sworn statement of accountability of the 
geotechnical engineering consultant who prepared it, shall 
be included in the submittals to be reviewed and examined 
by the building official or government authority in charge 
of issuing the relevant permits such as environmental 
compliance certificate and/or building permit. 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-13 


304.2 Presumptive Load-Bearing and Lateral 
^ Resisting Values 

When no exhaustive geotechnical site assessment and 
investigation is performed, especially when no in-situ or 
very limited tests are carried out, the presumptive load- 
bearing and lateral resisting values provided in Table 304-1 
shall be used. Use of these values requires that the 
foundation design engineer has, at the least, carried out an 
inspection of the site and has become familiar with the 
predominant soil or rock characteristics of the site. 

Presumptive load-bearing values shall apply to materials 
with similar physical characteristics and dispositions. Mud, 
organic silt, organic clays, peat or unprepared fill shall not 
be assumed to have a presumptive load-bearing capacity 
unless data from a geotechnical site assessment and 
investigation to substantiate the use of such a value are 
submitted. 

Table 304-1 Allowable Foundation and Lateral Pressure 


Class of Materials 7 

Allowable 

Foundation 

Pressure 2 

(kPa) 

Lateral 
Bearing 
Below Natural 
Grade 5 
(k Pa /m of 
depth) 

Lateral Sliding* 7 

- 

Coefficient 5 

Resistance 6 

(kPa) 

1 . “Intact” Tuffaceous Sandstone a 

1,000 

300 

- 

- 

2. “Lightly Weathered” Tuffaceous Sandstone b 

500 

150 

- 

- 

3. Sandy Gravel and /or Gravel(GW & GP) 

100 

30 - 

0.35 

- 

4. Well-graded Sand, Poorly-graded Sand, Silty Sand, 
Clayey Sand, Silty Gravel and Clayey Gravel (SW, 

SP, SM, SC, GM and GC) 

75 

25 

0.25 

* 

5. Clay, Sandy Clay, Silty Clay and Clayey Silt (CL, ML, 
MH, and CH) 

50 c 

15 

- 

7 


1 A geotechnical site investigation is recommended for soil classification (Refer to Section 303). 

All values of allowable foundation pressure are for footings having a minimum width of 300mm and a minimum depth of 300mm info the natural grade. Except as noted in 
Footnote ‘a an increase of 20% is allowed for each additional 300mm of width and/or depth to a maximum value of three times the designated value . An increase of one-third 
is permitted when using the alternate load combinations in Section 203,4 that include wind or earthquake loads 

■* The resistance values derived from the table are permitted to be increased by the tabular value for each additional 300 mm of depth to a maximum of 15 times the tabular 
value Isolated poles for uses such as flagpoles or signs and poles used to support buildings that are not adversely affected by a 12mm motion at (he ground surface due to 
short-term lateral loads are permitted to be designed using lateral-bearing values equal to (wo times the tabular values , 

* Lateral bearing and sliding resistance may be combined. 

* Coefficient to be multiplied by the dead load. 

Lateral sliding resistance value to be multiplied by the contact area. In no case shall the lateral sliding resistance exceed one-half the dead load. 
n Must satisfy both UCT mi „= 3Mpa and RQD >70 
b Must satisfy both UCT mi „= IMpa and RQD >50 
c No increase shall be allowed for an increase of width. 


For clay, sandy clay, silty clay and clayey silt, in no case 
shall the lateral sliding resistance exceed one-half the dead 
load. 

304.3 Minimum Allowable Pressures 

The recommended allowable foundation and lateral values 
shall be with the allowable stress design load combinations 
specified in Section 203.4. 

304.4 Foundations Adjacent to Existing 
Retaining/Basement Walls 

In cases where the adjacent building will have more 
basements than the proposed building, the foundation of the 
proposed building should be designed so as not to impart 
additional lateral earth pressures on the existing building. 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 



3-14 CHAPTER 3 - Earthworks and Foundations 


SECTION 305 

footings 

305.1 General 

Footings and foundations shall be constructed of masonry, 
concrete or treated wood in conformance with Chapters 4, 
6 and 7. Footings of concrete and masonry shall be of 
solid material. Foundations supporting wood shall extend 
at least 150 mm above the adjacent finish grade. Footings 
shall have a minimum depth as indicated in Table 305-1, 
unless another depth is warranted, as established by a 
foundation investigation. 

The provisions of this section do not apply to building and 
foundation systems in those areas subject to scour and 
water pressure by wind and wave action. Buildings and 
foundations subject to such loads shall be designed in 
accordance with approved national standard 


Table 305-1 Minimum Requirements for Foundations 1,2,3 


Number of 
Floors 

Supported by 
the Foundations 

Thickness of 
Foundation Wall 
(mm) 

Width 

of 

Footing 

(mm) 

Thickness 

of 

Footing 

(mm) 

Depth Below 
Undisturbed 
Ground 
Surface (mm ) 4 

Concrete 

Unit 

Masonry 

1 

150 

150 

300 

150 

300 

2 

200 

200 

375 

175 

450 

3 

250 

250 

450 

200 

600 


1 Where unusual conditions are found, footings and foundations shall 
be as required in Section 305. L 


2 The ground under the floor may be excavated to the elevation of the 
top of the footing. 

3 Foundation may support a roof in addition to the stipulated number 
of floors. Foundations supporting roofs only shall be as required for 
supporting one floor. 

305.2 Footing Design 

Except for special provisions of Section 307 covering the 
design of piles, all portions of footings shall be designed 
in accordance with the structural provisions of this code 
and shall be designed to minimize differential settlement 
when necessary and the effects of expansive soils when 
present. 

Slab-on-grade and mat-type footings for buildings located 
on expansive soils may be designed in accordance with 
the geotechnical recommendation as permitted by the 
building official. 


305.2.1 Design Loads 

Footings shall be designed for the most unfavorable load 
effects due to combinations of loads. The dead load is 
permitted to include the weight of foundations, footings 
and overlying fill. Reduced live loads as permitted in the 
Chapter on Loadings are permitted to be used in the 
design of footings. 

305.2.2 Vibratory Loads 

Where machinery operations or other vibratory loads or 
vibrations are transmitted to the foundations, 
consideration shall be given in the Report to address the 
foundation design to prevent detrimental disturbances to 
the soil. 

305.3 Bearing Walls 

Bearing walls shall be supported on masonry or concrete 
foundations or piles or other permitted foundation system 
that shall be of sufficient size to support all loads. 

Where a design is not provided, the minimum foundation 
requirements for stud bearing walls shall be as set forth in 
Table 305-1, unless expansive soils of a severity to cause 
differential movement are known to exist. 

Exceptions: 

1. A one-story wood or metal-frame building not used 
for human occupancy and not over 40 m 2 in floor 
area may be constructed with walls supported on a 
wood foundation plate permanently under the water 
table when permitted by the building official 

2. The support of buildings by posts embedded in earth 
shall be designed as specified in Section 305. 7. Wood 
posts or poles embedded in earth shall be pressure 
treated with an approved preservative. Steel posts or 
poles shall be protected as specified in Section 
306.10. 

305.4 Stepped Foundations 

Foundations for all buildings where the surface of the 
ground slopes more than 1 unit vertical in 10 units 
horizontal (10% slope) shall be level or shall be stepped 
so that both top and bottom of such foundation are level. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 



CHAPTER 3 - Earthworks and Foundations 3-15 



Figure 305-1 Setback Dimensions for Building Clearance for Stable Natural Slopes on Firm and Intact Ground 


305.5 Footings on or Adjacent to Slopes 

305.5.1 Scope 

The placement of buildings and structures on or adjacent 
to slopes steeper than 1 unit vertical in 3 units horizontal 
(33.3% slope) shall be in accordance with this section. 

305.5.2 Building Clearance from Ascending Slopes 

In general, buildings below slopes shall be set a sufficient 
distance from the slope to provide protection from slope 
drainage, erosion and shallow failures. Except as 
provided for in Section 305.5.6 and Figure 305-1, the 
following criteria will be assumed to provide this 
protection. Where the existing slope is steeper than 1 unit 
vertical in 1 unit horizontal (100% slope), the toe of the 
slope shall be assumed to be at the intersection of a 
horizontal plane drawn from the top of the foundation and 
a plane drawn tangent to the slope at an angle of 45 
degrees to the horizontal. Where a retaining wall is 
constructed at the toe of the slope, the height of the slope 
shall be measured from the top of the wall to the top of 
the slope. 


305.5.3 Footing Setback from Descending Slope 
Surface 

Footings on or adjacent to slope surfaces shall be founded 
in firm material with an embedment and setback from the 
slope surface sufficient to provide vertical and lateral 
support for the footing without detrimental settlement. 
Except as provided for in Section 305.5.6 and 
Figure 305-1, the following setback is deemed adequate 
to meet the criteria. Where the slope is steeper than 1 unit 
vertical in 1 unit horizontal (100% slope), the required 
setback shall be measured from an imaginary plane 45 
degrees to the horizontal, projected upward from the toe 
of the slope. 

305.5.4 Pools 

The setback between pools regulated by this code and 
slopes shall be equal to one half the building footing 
setback distance required by this section. That portion of 
the pool wall within a horizontal distance of 2 meters 
from the top of the slope shall be capable of supporting 
the water in the pool without soil support. 

305.5.5 Foundation Elevation 

On graded sites, the top of any exterior foundation shall 
extend above the elevation of the street gutter at point of 
discharge or the inlet of an approved drainage device a 
minimum of 300 mm plus 2 percent. The building official 
may permit alternate elevations, provided it can be 
demonstrated that required drainage to the point of 
discharge and away from the structure is provided at all 
locations on the site. 


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3-16 CHAPTER 3 - Earthworks and Foundations 


305.5.6 Alternate Setback and Clearance 


305.7.2 Design Criteria 


The Building Official may approve alternate setbacks and 
clearances. The building official may require an 
investigation and recommendation of a qualified engineer 
to demonstrate that the intent of this section has been 
satisfied. Such an investigation shall include 
consideration of material, height of slope, slope gradient, 
load intensity and erosion characteristics of slope 
material. 

305.5.7 Reinforced Slopes 

Footings on or adjacent to slopes reinforced using rock 
anchors, soils nails, geosynthethics or any other similar 
ground improvement technique shall be founded such that 
it does not interfere with or impair the function of the 
reinforcing elements. The Building Official may require 
the recommendation of a geotechnical engineer to 
demonstrate that the reinforced slope can safely carry the 
structural loads it will be subjected to. 

305.6 Foundation Plates or Sills 

Wood plates or sills shall be bolted to the foundation or 
foundation wall. Steel bolts with a minimum nominal 
diameter of 12 mm shall be used in Seismic Zone 2. Steel 
bolts with a minimum nominal diameter of 16 mm shall 
be used in Seismic Zone 4. Bolts shall be embedded at 
least 180 mm into the concrete or masonry and shall be 
spaced not more than 2 meters apart. There shall be a 
minimum of two bolts per piece with one bolt located not 
more than 300 mm or less than seven bolt diameters from 
each end of the piece. A properly sized nut and washer 
shall be tightened on each bolt to the plate. Foundation 
plates and sills shall be the kind of wood specified in 
Chapter 6. 

305.7 Designs Employing Lateral Bearing 

305.7.1 General 

Construction employing posts or poles as columns 
embedded in earth or embedded in concrete footings in 
the earth may be used and designed to resist both axial 
and lateral loads. The depth to resist lateral loads shall be 
determined by means of the design criteria established 
herein or other methods approved by the building official. 


305.7.2.1 Non-constrained 


The following formula may be used in determining the 
depth of embedment required to resist lateral loads where 
no constraint is provided at the ground surface, such as 
rigid floor or rigid ground surface pavement. 



(305-1) 


where: 


2.3 P 



b = diameter of round post or footing or diagonal 
dimension of square post or footing, m. 
d = depth of embedment in earth in m but not over 
3.5 m for purpose of computing lateral pressure, 
m 

fa = distance from ground surface to point of 
application of P, m 
p = applied lateral force, kN 

S ± = allowable lateral soil-bearing pressure as set 
forth in Table 304-1 based on a depth of one 
third the depth of embedment, kPa 
5 3 allowable lateral soil-bearing pressure as set 
forth in Table 304-1 based on a depth equal to 
the depth of embedment, kPa 

305.7.2.2 Constrained 


The following formula may be used to determine the 
depth of embedment required to resist lateral loads where 
constraint is provided at the ground surface, such as a 
rigid floor or pavement. 

7 Pk 

dr = 4.25— (305-2) 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-17 


305.7.2.3 Vertical load 

y The resistance to vertical loads is determined by the 
allowable soil-bearing pressure set forth in Table 304-1 . 

305.7.3 Backfill 

The backfill in the annular space around column not 
embedded in poured footings shall be by one of the 
following methods: 

1 . Backfill shall be of concrete with an ultimate strength 
of 15 MPa at 28 days. The hole shall not be less than 
100 mm larger than the diameter of the column at its 
bottom or 1 00 mm larger than the diagonal 
dimension of a square or rectangular column. 

2. Backfill shall be of clean sand. The sand shall be 
thoroughly compacted by tamping in layers not more 
than 200 mm in thickness. 

305.7.4 Limitations 

The design procedure outlined in this section shall be 
subject to the following limitations: 

305.7.4.1 The frictional resistance for retaining walls 
and slabs on silts and clays shall be limited to one half of 
the normal force imposed on the soil by the weight of the 
footing or slab. 

305.7.4.2 Posts embedded in earth shall not be used to 
provide lateral support for structural or nonstructural 
materials such as plaster, masonry or concrete unless 
bracing is provided. 

305.8 Grillage Footings 

When grillage footings of structural steel shapes are used 
on soils, they shall be completely embedded in concrete. 
Concrete cover shall be at least 150 mm on the bottom 
and at least 100 mm at all other points. 

305.9 Bleacher Footings 

Footings for open-air seating facilities shall comply with 
Chapter 3 . 

Exceptions: 

Temporary open-air portable bleachers may be supported 
upon wood sills or steel plates placed directly upon the 
ground surface , provided soil pressure does not exceed 
50 kPa. 


SECTION 306 

PILES-GENERAL REQUIREMENTS 

306.1 General 

Pile foundations shall be designed and installed on the 
basis of a foundation investigation as defined in 
Section 303 where required by the building official. 

The investigation and report provisions of Section 303 
shall be expanded to include, but not be limited to, the 
following: 

1. Recommended pile types and installed allowable 
axial capacities, and estimated settlement. 

2. Driving criteria. 

3. Installation procedures. 

4. Field inspection and reporting procedures (to include 
procedures for verification of the installed bearing 
capacity where required). 

5. Pile load test requirements. 

The use of piles not specifically mentioned in this chapter 
shall be permitted, subject to the approval of the building 
official upon submission of acceptable test data, 
calculations or other information relating to the properties 
and load-carrying capacities of such piles. 

306.2 Interconnection 

Individual pile caps- and caissons of every structure 
subjected to seismic forces shall be interconnected by ties. 
Such ties shall be capable of resisting, in tension or 
compression, a minimum horizontal force equal to 10 
percent of the largest column vertical load. 

Exception: 

Other approved methods may be used where it can be 
demonstrated that equivalent restraint can be provided . 

306.3 Determination of Allowable Loads 

The allowable axial and lateral loads on piles shall be 
determined by an approved formula, by a foundation 
investigation or by load tests. Static axial compressive 
pile load test shall be in accordance with ASTM Standard 
D-1143, and lateral load testing of piles shall conform 
with ASTM Standard D-3966. Dynamic pile tests shall 
be in accordance with ASTM Standard D-4945. Static 
axial tensile load testing to determine the uplift capacity 
of pile-soil systems shall be in accordance with ASTM 
Standard D-3689. 


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3-18 CHAPTER 3 - Earthworks and Foundations 


306.4 Static Load Test 

Static axial compressive pile load test shall be in 
accordance with ASTM Standard D-1143. The building 
official may require that the test be conducted under the 
supervision of a geotechnical engineer experienced and 
knowledgeable in the practice of static pile load testing 

When the allowable axial compressive load of a single 
pile is determined by a static load test, one of the 
following methods shall be used: 

Method 1. It shall not exceed 50 percent of the yield 
point under test load. The yield point shall be defined as 
that point at which an increase in load produces a 
disproportionate increase in settlement. 

Method 2. It shall not exceed one half of the load, which 
causes a net settlement, after deducting rebound, of 

0.03 mm/kN of test load, which has been applied for a 
period of at least 24 hours. 

Method 3. It shall not exceed one half of that load under 
which, during a 40-hour period of continuous load 
application, no additional settlement takes place. 

306.5 Dynamic Load Test 

High-strain dynamic load test may be used to determine 
the bearing capacity of piles, in accordance with 
ASTM Standard D-4945. The building official may 
require that the test be conducted by a geotechnical 
engineer experienced and knowledgeable in the practice 
of dynamic load testing. 

306.6 Column Action 

All piles standing unbraced in air, water or material not 
capable of lateral support shall conform with the 
applicable column formula as specified in this code. Such 
piles driven into firm ground may be considered fixed and 
laterally supported at 1.5 m below the ground surface and 
in soft material at 3 m from the ground surface unless 
otherwise prescribed by the building official after a 
foundation investigation by an approved agency. 


306.7 Group Action 

Consideration shall be given to the reduction of allowable 
pile load when piles are placed in groups. 

Where soil conditions make such load reductions 
advisable or necessary, the allowable axial and lateral 
loads determined for a single pile shall be reduced by any 
rational method or formula submitted to the building 
official. 

306.8 Lateral Loads 

The design of piles subjected to lateral loads shall be 
consistent with the design rules given Sections 306.1 
through 306.7, where applicable. For foundations 
involving piles subjected to lateral, the investigation and 
report provisions of Section 303 shall be expanded to 
include, but not be limited to: 

1. Allowable lateral load capacity of recommended pile 
type. 

2. Resulting lateral displacements at allowable lateral 
load. 

3. Lateral pile load test requirements. 

306.8.1 The design resistance of piles subjected to lateral 
loads, should be assessed based on one of the following 
failure mechanisms: 

1 . For short piles, rotation or translation as a rigid body 

2. For long slender piles, bending failure of the pile, 
accompanied by local yielding and displacement of 
the soil near the top of the pile. 

306.8.2 Pile Groups 

The group effects shall be considered when assessing the 
resistance of laterally loaded pile groups. 

306.8.3 Group interaction effects as well as head fixity 
shall be accounted for when deriving the lateral resistance 
of pile groups from results of load tests performed on 
individual piles. 

306.8.4 When assessing lateral load resistance from 
results of subsurface investigation and pile strength 
parameters, the transverse resistance of a pile or pile 
group shall be calculated using a compatible set of 
structural effects of actions, ground reactions and 
displacements, and consider the possibility of structural 
failure of the pile in the ground as well as the degree of 
freedom of rotation of piles at the connection with the 
structure. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-19 


306.9 Piles in Subsiding Areas 

^fVhere piles are driven through subsiding fills or other 
subsiding strata and derive support from underlying 
firmer materials, consideration shall be given to the 
downward frictional forces, which may be imposed on the 
piles by the subsiding upper strata. 

Where the influence of subsiding fills is considered as 
imposing loads on the pile, the allowable stresses 
specified in this chapter may be increased if satisfactory 
substantiating data are submitted. 

306.10 Water Jetting 

Installation of Piles by water shall not be used except 
where and as specifically permitted by the building 
official. When used, jetting shall be carried out in such a 
manner that the carrying capacity of existing piles and 
structures shall not be impaired. After withdrawal of the 
jet, piles shall be driven down until the required resistance 
is obtained. 

306.10 Protection of Pile Materials 

Where the boring records of site conditions indicate 
possible deleterious action oh pile materials because of 
soil constituents, changing water levels or other factors, 
such materials shall be adequately protected by methods 
or processes approved by the geotechnical engineer. 

The effectiveness of such methods or processes for the 
particular purpose shall have been thoroughly established 
by satisfactory service records or other evidence, which 
demonstrates the effectiveness of such protective 
measures. 


306.12 Allowable Loads 

The allowable loads based on soil conditions shall be 
established in accordance with Section 306, 

Exception: 

Any uncased cast-in-place pile may be assumed to 
develop a frictional resistance equal to one sixth of the 
bearing value of the soil material at minimum depth as set 
forth in Table 305-1 but not to exceed 25 kPa unless a 
greater value is allowed by the building official after a 
foundation investigation as specified in Section 303 is 
submitted Frictional resistance and bearing resistance 
shall not be assumed to act simultaneously unless 
recommended after a foundation investigation as 
specified in Section 303. 

306.13 Use of Higher Allowable Pile Stresses 

Allowable compressive stresses greater than those 
specified in Section 307 shall be permitted when 
substantiating data justifying such higher stresses are 
submitted to and approved by the building official. Such 
substantiating data shall be included in the foundation 
investigation report in accordance with Section 306. 1 . 


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3-20 CHAPTER 3 - Earthworks and Foundations 


SECTION 307 

#ILES-SPECIFIC REQUIREMENTS 

307.1 Round Wood Piles 

307.1.1 Material 

Except where untreated piles are permitted, wood piles 
shall be pressure treated. Untreated piles may be used 
only when it has been established that the cutoff will be 
below lowest groundwater level assumed to exist during 
the life of the structure. 

307.1.2 Allowable Stresses 

The allowable unit stresses for round woodpiles shall not 
exceed those set forth in Chapter 6. 

The allowable values listed in, for compression parallel to 
the grain at extreme fiber in bending are based on load 
sharing as occurs in a pile cluster. For piles which 
support their own specific load, a safety factor of 1.25 
shall be applied to compression parallel to the grain 
values and 1.30 to extreme fiber in bending values. 

307.2 Uncased Cast-In-Place Concrete Piles 
307.2.1 Material 

Concrete piles cast in place against earth in drilled or 
bored holes shall be made in such a manner as to ensure 
the exclusion of any foreign matter and to secure a full- 
sized shaft. 

The length of such pile shall be limited to not more than 
30 times the average diameter. Concrete shall have a 
specified compressive strength f f c of not less than 
17.5 MPa. 

Exception: 

The length of pile may exceed 30 times the diameter 
provided the design and installation of the pile foundation 
is in accordance with an approved foundation 
investigation report 


307.2.2 Allowable Stresses 

The allowable compressive stress in the concrete shall not 
exceed 0.33 f f c . The allowable compressive stress of 
reinforcement shall not exceed 34 percent of the yield 
strength of the steel or 175 MPa. 

307.3 Metal-Cased Concrete Piles 

307.3.1 Material 

Concrete used in metal-cased concrete piles shall have a 
specified compressive strength f r c of not less than 
17.5 MPa. 

307.3.2 Installation 

Every metal casing for a concrete pile shall have a sealed 
tip with a diameter of not less than 200 mm. 

Concrete piles cast in place in metal shells shall have 
shells driven for their full length in contact with the 
surrounding soil and left permanently in place. The shells 
shall be sufficiently strong to resist collapse and 
sufficiently watertight to exclude water and foreign 
material during the placing of concrete. 

Piles shall be driven in such order and with such spacing 
as to ensure against distortion of or injury to piles already 
in place. No pile shall be driven within four and one-half 
average pile diameters of a pile filled with concrete less 
than 24 hours old unless approved by the geotechnical 
engineer. 

307.3.3 Allowable Stresses 

Allowable stresses shall not exceed the values specified in 
Section 307.2.2, except that the allowable concrete stress 
may be increased to a maximum value of 0.40/^ for that 
portion of the pile meeting the following conditions: 

1. The thickness of the metal casing is not less than 
1.7 mm (No. 14 carbon sheet steel gage). 

2. The casing is seamless or is provided with seams of 
equal strength and is of a configuration that will 
provide confinement to the cast-in-place concrete. 

3. The specified compressive strength f' c shall not 
exceed 35 MPa and the ratio of steel minimum 
specified yield strength F y to concrete specified 
compressive strength f' c shall not be less than 6. 


4. The pile diameter is not greater than 400 mm. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-21 


307.4 Precast Concrete Piles 

307.4.1 Materials 

Precast concrete piles shall have a specified compressive 
strength f f c of not less than 20 MPa, and shall develop a 
compressive strength of not less than 20 MPa before 
driving. 

307.4.2 Reinforcement Ties 

The longitudinal reinforcement in driven precast concrete 
piles shall be laterally tied with steel ties or wire spirals. 
Ties and spirals shall not be spaced more than 75 mm 
apart, center to center, for a distance of 600 mm from the 
ends and not more than 200 mm elsewhere. The gage of 
ties and spirals shall be as follows: 

1. For piles having a diameter of 400 mm or less, wire 
shall not be smaller than 5.5 mm (No. 5 B.W.gage). 

2. For piles, having a diameter of more than 400 mm 
and less than 500 mm, wire shall not be smaller than 
6 mm (No. 4 B.W.gage). 

3. For piles having a diameter of 500 mm and larger, 
wire shall not be smaller than 6.5 mm 
(No. 3 B.W. gage). 

307.4.3 Allowable Stresses 

Precast concrete piling shall be designed to resist stresses 
induced by handling and driving as well as by loads. The 
allowable stresses shall not exceed the values specified in 
Section 307.2.2. 

307.5 Precast Prestressed Concrete Piles 
(Pretensioned) 

307.5.1 Materials 

Precast prestressed concrete piles shall have a specified 
compressive strength f r c of not less than 35 MPa and shall 
develop a compressive strength of not less than 27 MPa 
before driving. 

307.5.2 Reinforcement 

307.5.2.1 Longitudinal Reinforcement 

The longitudinal reinforcement shall be high-tensile 
seven-wire strand conforming to ASTM Standards. 
Longitudinal reinforcement shall be laterally tied with 
steel ties or wire spirals. 


307.5.2.2 Transverse Reinforcement 

Ties or spiral reinforcement shall not be spaced more than 
75 mm apart, center to center, for a distance of 600 mm 
from the ends and not more than 200 mm elsewhere. 

At each end of the pile, the first five ties or spirals shall be 
spaced 25 mm center to center. 

For piles having a diameter of 600 mm or less, wire shall 
not be smaller than 5.5 mm (No. 5 B.W.gage). 

For piles having a diameter greater than 600 mm but less 
than 900 mm, wire shall not be smaller than 6 mm 
(No. 4 B.W.gage). 

For piles having a diameter greater than 900 mm, wire 
shall not be smaller than 6.5 mm (No. 3 B.W. gauge). 

307.5.3 Allowable Stresses 

Precast prestressed piling shall be designed to resist 
stresses induced by handling and driving as well as by 
loads. The effective prestress in the pile shall not be less 
than 2.5 MPa for piles up to 10 m in length, 4 MPa for 
piles up to 15 m in length, and 5 MPa for piles greater 
than 1 5 meters in length. 

The compressive stress in the concrete due to externally 
applied load shall not exceed: 

fc — 0 . 33/^ — 0 . 'll f p C (307-1) 

where 

f pc = effective prestress stress on the gross 
section. 

Effective prestress shall be based on an assumed loss of 
200 MPa in the prestressing steel. The allowable stress in 
the prestressing steel shall not exceed the values specified 
in Section 418.6. 

307.5.4 Splicing 

Where required, splicing for concrete piles shall be by use 
of embedded and properly anchored thick steel plates at 
the ends being joined which shall then be fully welded, or 
by use of adequate sized dowel rods and steel receiving 
sleeves. The dowels and the faces shall then be joined by 
structural epoxy. Metal splice cans are not allowed. 


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3-22 CHAPTER 3 - Earthworks and Foundations 


307.6 Structural Steel Piles 
30f.6.1 Material 

Structural steel piles, steel pipe piles and fully welded 
steel piles fabricated from plates shall conform to one of 
the material specifications listed in Section 501.3. 

307.6.2 Allowable Stresses 

The allowable axial stresses shall not exceed 0.35 of the 
minimum specified yield strength F y or 85 MPa, 
whichever is less. 

Exception: 

When justified in accordance with Section 306.12 , the 
allowable axial stress may be increased above 85 MPa 
and 0. 35 F y , but shall not exceed 0. 5 F y . 

307.6.3 Minimum Dimensions 

Sections of driven H-piles shall comply with the 
following: 

1. The flange projection shall not exceed 14 times the 
minimum thickness of metal in either the flange or 
the web, and the flange widths shall not be less than 
80 percent of the depth of the section. 

2. The nominal depth in the direction of the web shall 
not be less than 200 mm. 

3. Flanges and webs shall have a minimum nominal 
thickness of 10 mm. 

Sections of driven pipe piles shall have an outside 
diameter of not less than 250 mm and a minimum 
thickness of not less than 6 mm. 

307.7 Concrete-Filled Steel Pipe Piles 
307.7.1 Material 

The steel pipe of concrete-filled steel pipe piles shall 
conform to one of the material specifications listed in 
Section 501.3. The concrete in concrete-filled steel pipe 
piles shall have a specified compressive strength f f c of not 
less than 17.5 MPa. 


307.7.2 Allowable Stresses 

The allowable axial stresses shall not exceed 0.35 of the 
minimum specified yield strength F y of the steel or 0.33 
of the specified compressive strength f f c of concrete, 
provided F y shall not be assumed greater than 250 MPa 
for computational purposes. 



Exception: 


When justified in accordance with Section 306.12, the 
allowable stresses may be increased to 0. 50 F y . 


307.7.3 Minimum Dimensions 

Driven piles of uniform section shall have a nominal 
outside diameter of not less than 200 mm. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




CHAPTER 3 - Earthworks and Foundations 3-23 


SECTION 308 

FOUNDATION CONSTRUCTION- 
SEISMIC ZONE 4 

308.1 General 

In Seismic Zones 4, the further requirements of this 
section shall apply to the design and construction of 
foundations, foundation components and the connection 
of superstructure elements thereto. See Section 421.10 
for additional requirements for structural concrete 
foundations resisting seismic forces. 

308.2 Foundation and Geotechnical Investigations 

Where a structure is determined to be in Seismic Zone 4 
in accordance with Section 208.4, an investigation shall 
be conducted and shall include an evaluation of the 
following potential hazards resulting from earthquake 
motions: slope instability, liquefaction and surface rupture 
due to faulting or lateral spreading. 

In addition, the following investigations shall also be met: 

1 . A determination of lateral pressures on basement and 
retaining walls due to earthquake motions. 

2. An assessment of potential consequences of any 
liquefaction and soil strength loss, including 
estimation of differential settlement, lateral 
movement or reduction in foundation soil-bearing 
capacity, and shall address mitigation measures. Such 
measures shall be given consideration in the design 
of the structure and can include but are not limited to 
ground stabilization, selection of appropriate 
foundation type and depths, selection of appropriate 
structural systems to accommodate anticipated 
displacements or any combination of these measures. 
The potential for liquefaction and soil strength loss 
shall be evaluated for site peak ground acceleration 
magnitudes and source characteristics consistent with 
the design earthquake ground motions. Peak ground 
acceleration shall be determined from a site-specific 
study taking into account soil amplification effects, 
as specified in Section 208.4. 


308.3 Footing Foundations 

Where a structure is assigned to Seismic Zone 4 in 
accordance with Section 208.4, individual spread footings 
founded on soil defined in Section 208.4.3 as Soil profile 
Type S E or S F shall be interconnected by ties. Ties shall 
be capable of carrying, in tension or compression, unless 
it is demonstrated that equivalent restraint is provided by 
reinforced concrete beams within slabs on grade or 
reinforced concretes labs on grade. 

308.4 Pier and Pile Foundations 

Where a structure is assigned to Seismic Zone 4 in 
accordance with Section 208.4, the following shall apply. 
Individual pile caps, piers or piles shall be interconnected 
by ties. Ties shall be capable of carrying, in tension and 
compression, unless it can be demonstrated that 
equivalent restraint is provided by reinforced concrete 
beams within slabs on grade, reinforced concrete slabs on 
grade, confinement by competent rock, hard cohesive 
soils or very dense granular soils. Concrete shall have a 
specified compressive strength of not less than 3,000 psi 
(20.68 MPa) at 28days. 

Exception: 

Piers supporting foundation walls , isolated interior posts 
detailed so the pier is not subject to lateral loads , lightly 
loaded exterior decks and patios and occupancy category 
IV and V specified in Section 103 not exceeding two 
stories of light-frame construction, are not subject to 
interconnection if it can be shown the soils are of 
adequate stiffness ; subject to the approval of the building 
official. 


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3-24 CHAPTER 3 - Earthworks and Foundations 


308.4.1 Connection to Pile Cap 

> 

For piles required to resist uplift forces or provide 
rotational restraint, design of anchorage of piles into the 
pile cap shall be provided considering the combined effect 
of axial forces due to uplift and bending moments due to 
fixity to the pile cap. Anchorage shall develop a minimum 
of 25 percent of the strength of the pile in tension. 
Anchorage into the pile cap shall be capable of 
developing the following: 

1 . In the case of uplift, the lesser of the nominal tensile 
strength of the longitudinal reinforcement in a 
concrete pile, or the nominal tensile strength of a 
steel pile, or the pile uplift soil nominal strength 
factored by 1.3 or the axial tension force resulting 
from the load combinations of Section 203. 

2. In the case of rotational restraint, the lesser of the 
axial and shear forces, and moments resulting from 
the load combinations of Section 203 or development 
of the full axial, bending and shear nominal strength 
of the pile. 

308.4.2 Design Details for Piers, Piles and Grade 
Beams 

Piers or piles shall be designed and constructed to 
withstand maximum imposed curvatures from earthquake 
ground motions and structure response. Curvatures shall 
include free-field soil strains modified for soil-pile- 
structure interaction coupled with pier or pile 
deformations induced by lateral pier or pile resistance to 
structure seismic forces. Concrete piers or piles on soil 
type S E or sites, as determined in Section 208.4.3, 
shall be designed and detailed in accordance with 
Sections 410 within seven pile diameters of the pile cap 
and the interfaces of soft to medium stiff clay or 
liquefiable strata. Grade beams shall be designed as 
beams in accordance Section 4. When grade beams have 
the capacity to resist the forces from the load 
combinations in Section 203. 

308.4.3 Flexural Strength 

Where the vertical lateral-force-resisting elements are 
columns, the grade beam or pile cap flexural strengths 
shall exceed the column flexural strength. The connection 
between batter piles and grade beams or pile caps shall be 
designed to resist the nominal strength of the pile acting 
as a short column. Batter piles and their connection shall 
be capable of resisting forces and moments from the load 
combinations of Section 203. 


308.5 Driven Pile Foundations 

308.5.1 Precast Concrete Piles 

Where a structure is assigned to Seismic Zone 4, a 
minimum longitudinal steel reinforcement ratio of 0.01 
shall be provided for precast non-prestressed concrete 
piles. The longitudinal reinforcing shall be confined with 
closed ties or equivalent spirals of a minimum 3/8 in 
(10 mm) diameter. Transverse confinement reinforcing 
shall be provided at a maximum spacing of eight times the 
diameter of the smallest longitudinal bar, but not to 
exceed 6 in. (152 mm), within three pile diameters of the 
bottom of the pile cap. Outside of the confinement region, 
closed ties or equivalent spirals shall be provided at a 16 
longitudinal-bar-diameter maximum spacing, but not 
greater than 8 in. (200 mm). Reinforcement shall be full 
length. 

For Site Classes D through F, Transverse confinement 
reinforcement consisting of closed ties or equivalent 
spirals shall be provided in accordance with 
Sections 2 1 .6.4.2 through 2 1 .6.4.4 of ACI 318 for the full 
length of the pile. 

In other than Site Classes E or F, the specified transverse 
confinement reinforcement shall be provided within three 
pile diameters below the bottom of the pile cap, but it is 
permitted to use a transverse reinforcing ratio of not less 
than one-half of that required in Section 21.6.4.4(a) of 
ACI 3 1 8 throughout the remainder of the pile length. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 3 - Earthworks and Foundations 3-25 


308.5.2 Precast Prestressed Piles 


but not less than: 


Wfiere a structure is assigned to Seismic Zone 4, the 
following shall apply: 

For the upper 20 ft (6 m) of precast prestressed piles, the 
minimum volumetric ratio of spiral reinforcement shall 
not be less than 0.007 or the amount required by the 
following equation: 


Ps 



1 1.4 P 

2 + 7?v 


and need not exceed: 


Ps = 0.021 

where 


(308.5.3) 


(308.5.4) 


Ps = 0. 12f' c /f yh (308.5.1) 

where 

fc = Specified compressive strength of 

concrete, MPa 

fyh = Yield strength of spiral reinforcement, 

586 MPa 

p s - Spiral reinforcement index 

(volume spiral/volume of core) 

A minimum of one-half of the volumetric ratio of spiral 
reinforcement required by Eq. 308.5.1 shall be provided 
for the remaining length of the pile. 

Requirements of ACI 318, Chapter 2 1 , need not apply. 

Where the total pile length in the soil is 35 It (10.668 mm) 
or less, the lateral transverse reinforcement in the ductile 
region shall occur through the length of the pile. Where 
Ihe pile length exceeds 35 ft (10.668 mm), the ductile pile 
region shall be taken as the greater of 3511 ( 1 0,668 mm) or 
ihe distance from the underside of the pile cap to the point 
of zero curvature plus three times the least pile 
dimension. 

In the ductile region, the center-to-center spacing of the 
spirals or hoop reinforcement shall not exceed one-fifth 
of the least pile dimension, six times the diameter of the 
longitudinal strand, or 8 in (203 mm), whichever is 
smaller. 

Spiral reinforcement shall be spliced by lapping one full 
turn, by welding, or by the use of a mechanical connector. 
Where spiral reinforcement is lap spliced, the ends of the 
spiral shall terminate in a seismic hook in accordance 
with ACI 318, except that the bend shall be not less than 
135°. 


Where the transverse reinforcement consists of circular 
spirals, the volumetric ratio of spiral transverse 
reinforcement in the ductile region shall comply with the 
following: 


p s = 0.25 A 

Jyk 



0 


1 1 . 4P 

2 + 7Tv 


(308.5.2) 


A g - Pile cross-sectional area, mm 2 

A c fi ~~ Core area defined by spiral outside diameter, 
mm 2 

f c ~ Specified compressive strength of concrete, 

MPa <41.4 MPa 

fyh - Yield strength of spiral reinforcement 
<586 MPa 

P — Axial load on pile resulting from the load 
combination 1 2D + 0.5Z, + 1 .0 E, kN 
Ps — Volumetric ratio (volume of spiral/ volume of 
core) 

This required amount of spiral reinforcement is permitted 
to be obtained by providing an inner and outer spiral. 

When transverse reinforcement consists of rectangular 
hoops and cross ties, the total cross-sectional area of 
lateral transverse reinforcement in the ductile region with 

spacings, and perpendicular to dimension, h c , shall 
conform to: 




1 

1.4 

2 f c A 


but not less than: 

Aa = 0. 12 sh c Cp- 


yh 


1 1.4 P 

2 + 7^7j 


l gJ 

(308.5.5) 

(308.5.6) 


where 

fyh 

hr 


P 

J ls/i 

A 

f'c 


< 483 MPa 

Cross-sectional dimension of pile core 
measured center to center of hoop 
reinforcement, mm 

Spacing of transverse reinforcement 
measured along length of pile, mm 
Axial load, N 

Cross-sectional area of transverse 
reinforcement, mm 2 
Gross area of pile, mm 2 

Specified compressive strength of concrete, 
MPa 


National Structural Code of the Philippines Volume I, 7th Edition, 2015 


3-26 CHAPTER 3 - Earthworks and Foundations 


The hoops and cross ties shall be equivalent to deformed 
bars not less than 10 mm in size. Rectangular hoop ends 
shall terminate at a corner with seismic hooks. 

Outside of the length of the pile requiring transverse 
confinement reinforcing, the spiral or hoop reinforcing 
with a volumetric ratio not less than one-half of that 
required for transverse confinement reinforcing shall be 
provided. 

308.6 Cast-In-Place Concrete Foundations 

Where a structure is assigned to Seismic Zone 4 a 
minimum longitudinal reinforcement ratio of 0.005 shall 
be provided for uncased cast-in-place drilled or augered 
concrete piles, piers or caissons in the top one-half of the 
pile length a minimum length of 10 feet (3,048 mm) 
below ground or throughout the flexural length of the pile, 
whichever length is greatest. The flexural length shall be 
taken as the length of the pile to a point where the 
concrete section cracking moment strength multiplied by 
0.4 exceeds the required moment strength at that point. 
There shall be a minimum of four longitudinal bars with 
transverse confinement reinforcement provided in the pile 
within three times the least pile dimension of the bottom 
of the pile cap. A transverse spiral reinforcement ratio of 
not less than one-half of that required in Section 410 for 
other than Soil Profile Type S E , S F or as determined in 
Section 208.4.3 or liquefiable sites is permitted. Tie 
spacing throughout the remainder of the concrete section 
shall neither exceed 12-longitudinal-bar diameters, 
one-half the least dimension of the section, nor 12 inches 
(305 mm). Ties shall be a minimum of 10mm bars for 
piles with a least dimension up to 20 inches (508 mm), 
and 12 mm bars for larger piles. 


SECTION 309 
SPECIAL FOUNDATION, 

SLOPE STABILIZATION AND 
MATERIALS OF CONSTRUCTION 

309.1 Special Foundation Systems 

Special foundation systems or materials other than 
specified in the foregoing Sections may be introduced 
provided that such systems can be supported by 
calculations and theory to be providing safe foundation 
systems and when approved by the Engineer of record. 
Materials for incorporation into the foundation should 
have proven track record of successful usage in similar 
applications. 

309.2 Acceptance and Approval 

Structure support on improved ground using such special 
systems or proprietary systems may be approved subject 
to submittal of calculations and other proof of acceptance 
and successful usage. 

309.3 Specific Applications 

Specialty foundation systems may be applied or used 
specifically to address any or combinations of the 
following: Bearing Capacity Improvement, Liquefaction 
mitigation, slope stability enhancement, control and/or 
acceleration of Consolidation settlements or immediate 
settlements, increase in soil shear capacity, increased 
pullout or overturniug capacity, special anchors in soil 
and rock and other beneficial effects. Controlled low 
strength materials (CLSM) to reduce fill loads may be 
allowed for use where applicable. 



Association of Structural Engineers of the Philippines, Inc. (ASEP) 


N8CP Cl 01-1 5 


Chapter 4 


STRUCTURAL CONCRETE 


NATIONAL STRUCTURAL CODE OF THE PHILIPPINES 
VOLUME I 

BUILDINGS, TOWERS AND 
OTHER VERTICAL STRUCTURES 

SEVENTH EDITION, 2015 


Association of Structural Engineers of the Philippines, Inc. 
Suite 713, Future Point Plaza Condominium 1 
112 Panay Avenue, Quezon City, Philippines 1100 

Tel. No. : (+632) 410-0483 
Fax No. : (+632) 411-8606 
Email: aseponiine@gmail.com 
Website: http:/Avww.aseponline.org 



National Structural Code of the Philippines Volume I, 7th Edition, 2015 




CHAPTER 4 - Structural Concrete 4-1 


Table of Contents 

SECTION 401. , ? 

GENERAL REQUIREMENTS 

401.1 Scope. . .. _ 7 

401.2 General , ... ... 7 

401.3 Purpose ... ..... . ....... ..... * 7 

401.4 Applicability lfv w#; v; " 7 

401.5 Interpretation.......,,. .. 8 

401.6 Building Official .. g 

401.7 Licensed Design Professional , . . g 

401.8 Construction Documents and Design Records 9 

401.9 Testing and Inspection ........ ...... 9 

40 1 . 1 0 Approval of Special Systems of Design, Construction, or Alternative Construction Materials 9 

401.11 Provisions for Earthquake Resistance ......... 9 

SECTION 402 9 

NOTATION AND TERMINOLOGY 

402.1 Scope . ^ a 9 

402.2 Notation . t 9 

402.3 Terminology .. . .. ... 20 

SECTION 403 w 28 

REFERENCED STANDARDS 28 

403.1 Scope 28 

403.2 Referenced Standards 28 

SECTION 404 

STRUCTURAL SYSTEM REQUIREMENTS 

404.1 Scope 3 ] 

404.2 Materials ~ 31 

404.3 Design Loads 31 

404.4 Structural System and Load Paths 31 

404.5 Structural Analysis 32 

404.6 Strength . ....... 32 

404.7 Serviceability ...... 32 

404.8 Durability 32 

404.9 Sustainability 33 

404.10 Structural Integrity ... 33 

404.1 1 Fire Resistance „ .. 33 

404.12 Requirements for Specific Types of Construction ........... 33 

404. 1 3 Construction and Inspection . 34 

404.14 Strength Evaluation of Existing Structures 34 

SECTION 405 34 

LOADS „.34 

405.1 Scope .*■*, ........... 34 

405.2 General 34 

405.3 Load Factors and Combinations 34 

SECTION 406 . # 36 

STRUCTURAL ANALYSIS * „ 36 


National Structural Code of the Philippines Volume I, 7 th Edition, 2015 


4-2 


CHAPTER 4 - Structural Concrete 


406.1 Scope * * * * * 

£ 06.2 General * ■ * * **"■ * 

406.3 Modeling Assumptions . •>**—■ 

406.4 Arrangement of Live Load - — — — 

406.5 Simplified Method of Analysis for Non-Prestressed Continuous Beams and One-way Slabs 

406.6 First-order Analysis 

406.7 Elastic Second-order Analysis — - * 

406.8 Inelastic Second-Order Analysis » * 

406.9 Acceptability of Finite Element Analysis — 

SECTION 407 


36 

36 

37 
37 

37 

38 
41 

41 

42 

,42 


ONE-WAY SLABS 


42 


407.1 Scope * 

407.2 General 

407.3 Design Limits 

407.4 Required Strength 

407.5 Design Strength 

407.6 Reinforcement Limits 

407.7 Reinforcement Detailing, 


42 

42 

42 

43 

44 

44 

45 


SECTION 408 


47 


TWO-WAY SLABS 

408.1 Scope 

408.2 General 

408.3 Design Limits 

408.4 Required Strength. * 

408.5 Design Strength 

408.6 Reinforcement Limits 

408.7 Reinforcement Detailing 

408.8 Non-Prestressed Two-Way Joist Systems 

408.9 Lift-slab Construction 

408.10 Direct Design Method 

408 . 1 1 Equivalent Frame Method 

SECTION 409 


47 

47 

47 

.48 

49 

.51 

.52 

.52 

.56 

.57 

.57 

.60 

.61 


BEAMS 


409.1 Scope 

409.2 General 

409.3 Design Limits * 

409.4 Required Strength * 

409.5 Design Strength * 

409.6 Reinforcement Limits 

409.7 Reinforcement Detailing..* * 

409.8 Non-Prestressed One-way Joist Systems 

409.9 Deep Beams — 

SECTION 410 


61 

61 

62 

63 

63 

64 

65 
,68 
69 

.70 


COLUMNS 


410.1 Scope 

410.2 General 

410.3 Design Limits 

410.4 Required Strength 

410.5 Design Strength ,.*,****. 

4 1 0.6 Reinforcement Limits 


70 

70 

70 

70 

71 
71 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 4 - Structural Concrete 4-3 


410.7 Reinforcement Detailing ..... . ..... . — — * . ...71 

SECTION 411 74 

WALLS 74 

411.1 Scope. ......... ..... . . ...... • ,«»> 74 

41 1 .2 General . . ; * 74 

411.3 Design Limits * v 74 

41 1.4 Required Strength ..... ............ * < 75 

41 1.5 Design Strength .. ■».*»..*. . 75 

411.6 Reinforcement Limits.. 76 

41 1 .7 Reinforcement Detailing . ........ ... 77 

411.8 Alternative Method for Out-of-Plane Slender Wall Analysis * 78 

SECTION 412 79 

DIAPHRAGMS 79 

412.1 Scope . 79 

412.2 General > ■■■■■ 79 

412.3 Design Limits ... 80 

412.4 Required Strength 80 

412.5 Design Strength * «. - . 80 

412.6 Reinforcement Limits . 82 

412.7 Reinforcement Detailing „ — 82 

SECTION 413 83 

FOUNDATIONS 83 

413.1 Scope . .. * 83 

413.2 General «, >. 83 

413.3 Shallow Foundations ..... * * 84 

413.4 Deep Foundations 85 

SECTION 414 86 

PLAIN CONCRETE 86 

414.1 Scope 86 

414.2 General . — 86 

414.3 Design Limits . v ,.86 

414.4 Required Strength . * * 87 

414.5 Design Strength * 88 

414.6 Reinforcement Detailing * * .. 89 

SECTION 415 90 

BEAM-CONCRETE AND 90 

SLAB-COLUMN JOINTS 90 

415.1 Scope - * * 90 

415.2 General - 90 

415.3 Transfer of Column Axial Force through the Floor System. 90 

415.4 Detailing of Joints «. - 90 

SECTION 416 91 

CONNECTION BETWEEN MEMBERS 91 

416.1 Scope 91 

416.2 Connections of Precast Members. , ; * » 91 

416.3 Connections to Foundations * . 92 

416.4 Horizontal Shear Transfer in Composite Concrete Flexural Members * 94 


National Structural Code of the Philippines Volume ! ; 7 lh Edition, 2015 


4-4 CHAPTER 4 - Structural Concrete 


416.5 Brackets and Corbels . . . — * - 95 

SECTION 417 97 

ANCHORING TO CONCRETE 97 

417.1 Scope * * - 97 

417.2 General * * ...... » *■ - — 98 

417.3 General Requirements for Strength of Anchors * ... - 100 

417.4 Design Requirements for Tensile Loading * ■* 102 

417.5 Design Requirements for Shear Loading .. - — - 105 

417.6 Interaction of Tensile and Shear Forces . - — ■ 108 

417.7 Required Edge Distances, Spacings, and Thicknesses to Preclude Splitting Failure .. 108 

417.8 Installation and Inspection of Anchors 109 

SECTION 418 HO 

EARTHQUAKE-RESISTANT STRUCTURES 110 

418.1 Scope .«• v * 110 

418.4 Intermediate Moment Frames * * * — 1 1 1 

418.5 Intermediate Precast Structural Walls 113 

418.6 Beams of Special Moment Frames *•,<■«■ * 1 13 

418.7 Columns of Special Moment Frames — * — - 115 

418.8 Joints of Special Moment Frames...... .....117 

418.9 Special Moment Frames Constructed Using Precast Concrete... 119 

418.10 Special Structural Walls - * * - - * — * 1 19 

418.11 Special Structural Walls Constructed Using Precast Concrete . 123 

418.12 Diaphragms and Trusses . 123 

418.13 Foundations — ■■■■* 125 

418.14 Members Not Designated as Part of the Seismic-Force-Resisting System* 127 

SECTION 419 * * 128 

CONCRETE: DESIGN AND DURABILITY REQUIREMENTS * * - 128 

419.1 Scope * * 128 

419.2 Concrete Design Properties >. 128 

419.3 Concrete Durability Requirements -■■■- — * 129 

419.3.1 Exposure Categories and Classes - * .129 

419.4 Grout Durability Requirements . ....131 

SECTION 420 131 

STEEL REINFORCEMENT PROPERTIES, DURABILITY, AND EMBEDMENTS 131 

420.1 Scope.. - « .. * — * 131 

420.2 Non-Prestressed Bars and Wires .....131 

420.3 Prestressing Strands, Wires, and Bars .................. **.<»...» ... 132 

420.5 Headed Shear Stud Reinforcement... * 136 

420.6 Provisions for Durability of Steel Reinforcement * - 1 36 

420.7 Embedments * . 138 

SECTION 421 139 

STRENGTH REDUCTION FACTORS 139 

421.1 Scope - * *-139 

SECTION 422 142 

SECTIONAL STRENGTH 142 

422.1 Scope . - - * 142 

422.2 Design Assumptions for Moment and Axial Strength ... 142 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 4 - Structural Concrete 4-5 


422.3 Flexural Strength 

422.4 Axial Strength or Combined Flexural and Axial Strength . 

422.5 One-way Shear Strength 

422.6 Two-Way Shear Strength 

422.7 Torsional Strength 

422.8 Bearing 

422.9 Shear Friction 

SECTION 423 


. 143 
. 143 
,144 
,147 
, 150 
,152 
152 

.154 


STRUT-AND-TIE MODELS 




423.1 

423.2 

423.3 

423.4 

423.5 

423.6 

423.7 

423.8 

423.9 


Scope 

General 

Design Strength 

Strength of Struts 

Reinforcement Crossing Bottle-Shaped Struts 

Strut Reinforcement Detailing 

Strength of Ties 

Tie Reinforcement Detailing 

Strength of Nodal Zones 



SECTION 424 


157 


SERVICEABILITY REQUIREMENTS 


157 


424.1 

424.2 

424.3 

424.4 

424.5 


Scope...,. . 

Deflections Due to Service-Level Gravity Loads 

Distribution of Flexural Reinforcement in One-Way Slabs and Beams 

Shrinkage and Temperature Reinforcement 

Permissible Stresses in Prestressed Concrete Flexural Members 


157 

157 

158 

159 

160 


SECTION 425 


161 


REINFORCEMENT DETAILS 161 

425.1 Scope ,, * 161 

425 .2 Minimum Spacing of Reinforcement , j 6 1 

425.3 Standard Hooks, Seismic Hooks, Crossties, and Minimum Inside Bend Diameters. .... 162 

425.4 Development of Reinforcement ] 63 

425.5 Splices * .. 167 

425.6 Bundled Reinforcement * 169 

425.7 Transverse Reinforcement 169 

425.8 Post-Tensioning Anchorages and Couplers . 1 72 

425.9 Anchorage Zones for Post-Tensioned Tendons 1 72 

SECTION 426 175 


CONSTRUCTION DOCUMENTS AND INSPECTION 


..175 


426.1 

426.2 

426.3 

426.4 

426.5 

426.6 

426.7 

426.8 

426.9 

426.10 

426.11 

426.12 


Scope „„ 

Design Criteria 

Member Information 

Concrete Materials and Mixture Requirements 

Concrete Production and Construction 

Reinforcement Materials and Construction Requirements 

Anchoring to Concrete 

Embedments 

Additional Requirements for Precast Concrete 

Additional Requirements for Prestressed Concrete 

Formwork 

Concrete Evaluation and Acceptance 



National Structural Code of the Philippines Volume I, 7 tn Edition, 2015 


CHAPTER 4 - Structural Concrete 4-5 


422.3 Flexural Strength ... , _ _ __ 143 

y 422.4 Axial Strength or Combined Flexural and Axial Strength ..... I 43 

422.5 One-way Shear Strength 1 44 

422.6 Two-Way Shear Strength . ,, ¥ ' 14 y 

422.7 Torsional Strength . 250 

422.8 Bearing . t v: " ^2 

422.9 Shear Friction .... 2^2 

SECTION 423 154 

STRUT- AND-TIE MODELS 154 

423.1 Scope * , 2^ 4 

423.2 General ,,,, . _ . 2^4 

423.3 Design Strength ,. _ 254 

423.4 Strength of Struts _ 254 

423.5 Reinforcement Crossing Bottle-Shaped Struts. . . 255 

423.6 Strut Reinforcement Detailing . p 255 

423.7 Strength of Ties 255 

423.8 Tie Reinforcement Detailing * „„ pjr a 256 

423.9 Strength of Nodal Zones...., ...... 256 

SECTION 424 

SERVICEABILITY REQUIREMENTS 

424.1 Scope 157 

424.2 Deflections Due to Service-Level Gravity Loads , ...... __ 157 

424.3 Distribution of Flexural Reinforcement in One-Way Slabs and Beams.. „ 158 

424.4 Shrinkage and Temperature Reinforcement 159 

424.5 Permissible Stresses in Prestressed Concrete Flexural Members , 160 

SECTION 425 

REINFORCEMENT DETAILS 

425.1 Scope .. ..... . . . 16 1 

425.2 Minimum Spacing of Reinforcement K * 16 i 

425.3 Standard Hooks, Seismic Hooks, Crossties, and Minimum Inside Bend Diameters 162 

425.4 Development of Reinforcement . I 63 

425.5 Splices . ..... . . , 16 7 

425.6 Bundled Reinforcement „ t ,,.169 

425.7 Transverse Reinforcement... . ^ I 69 

425.8 Post-Tensioning Anchorages and Couplers _ 172 

425.9 Anchorage Zones for Post-Tensioned Tendons 172 

SECTION 426 

CONSTRUCTION DOCUMENTS AND INSPECTION 

426.1 Scope. f : ^. w# 175 

426.2 Design Criteria . K iv . 175 

426.3 Member Information 175 

426.4 Concrete Materials and Mixture Requirements . 175 

426.5 Concrete Production and Construction 178 

426.6 Reinforcement Materials and Construction Requirements 181 

426.7 Anchoring to Concrete .. 182 

426.8 Embedments ; 182 

426.9 Additional Requirements for Precast Concrete . 1 83 

426.10 Additional Requirements for Prestressed Concrete 183 

426.11 Formwork . 184 

426. 12 Concrete Evaluation and Acceptance 1 85 


National Structural Code of the Philippines Volume I, 7 th Edition, 2015 


4-6 


CHAPTER 4 - Structural Concrete 


_ ...187 

426.13 Inspection - " ' # 188 

SECTION 427 1RR 

STRENGTH EVALUATION OF EXISTING STRUCTURES ^ ^ 

427.1 Scope 188 

427.2 General 188 

427.3 Analytical Strength Evaluation ^ 189 

427.4 Strength Evaluation by Load Test 1 90 

427.5 Reduced Load Rating 

SECTION 428 

building code requirements for concrete thin shells w 

1^1 

428.1 Scope and Definitions - 191 

428.2 Analysis and Design * * * "" 192 

428.3 Design Strength * * . ..192 

428 4 1 Cast-in-place Non-P restressed Concrete » - * 1 92 

428.4.4 Specified Concrete Cover Requirements tor Corrosive Environm ■■■■■■ ] ^ 

428.5 Shell Reinforcement 194 

428.6 Construction 

SECTION 429 194 

ALTERNATE DESIGN METHOD | ^ 

429.1 Notations 194 

429.2 Scope 194 

429.3 General 194 

429.4 Permissible Service Load Stresses 1 95 

429.5 Development and Splices of Reinforcement * 195 

429.7 Compression Members With or Without Flexure " 195 

429.8 Shear and Torsion 

APPENDIX A 201 

APPENDIX 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER4 - Structural Concrete 4-7 


SECTION 401 

/GENERAL REQUIREMENTS 

401.1 Scope 

401.1.1 This section addresses (a) to (h): 

a. General requirements of this Chapter; 

b. Purpose of this Chapter; 

c. Applicability of this Chapter; 

d. Interpretation of this Chapter; 

e. Definition of building official and the licensed design 
professional; 

f. Construction documents; 

g. Testing and inspection; 

h. Approval of special systems of design, construction, 
or alternative construction materials. 

401.2 General 

401.2.1 Chapter 4 refers to the structural concrete 
provision of the National Structural Code of the 
Philippines, Volume I (NSCP Vol. I), 7 th Edition and may 
be cited as such, and will be referred to herein as “this 
Code”. 

401.2.2 This chapter provides minimum requirements 
for the design and construction of structural concrete 
elements of any building or other structure under 
requirements of the National Building Code of the 
Philippines of which this chapter of the National 
Structural Code of the Philippines, Volume I, forms a 
part. This chapter also covers the strength evaluation of 
existing concrete structures. 

For structural concrete, f f c shall not be less than 17 MPa. 
No maximum value of f f c shall apply unless restricted by 
a specific code provision. 

401.2.3 This chapter is in English, with SI units, 
published by the Association of Structural Engineers of 
the Philippines, Inc. 

401.2.4 In case of conflict between this edition and other 
earlier versions, this latest version governs. 


401.2.5 This chapter provides the minimum requirements 
for the materials, design, construction, and strength 
evaluation of structural concrete members and systems in 
any structure designed and constructed under the 
requirements of the general building code. 

401.2.6 Modifications to this Code that are adopted by a 
particular government agency or local government are 
part of that organization’s requirements, but are not part 
of this Code. 

401.2.7 This chapter provides the minimum requirements 
for the materials, design, construction* and strength 
evaluation of structural concrete members and systems in 
any structure within this Code. 

401.3 Purpose 

401.3.1 The purpose of this chapter is to provide for 
public health and safety by establishing minimum 
requirements for strength, stability, serviceability, 
durability, and integrity of concrete structures. 

401.3.2 This chapter does not address all design 
considerations. 

401.3.3 Construction means and methods are not 
addressed in this section. 

40 1 .4 Applicability 

401.4.1 This chapter shall apply to concrete structures 
designed and constructed under the requirements of the 
general building code.' 

401.4.2 Applicable provisions of this chapter shall be 
permitted to be used for structures not governed by the 
general building code. 

401.4.3 The design of thin shells and folded plate 
concrete structures shall be in accordance with Section 
428. 

401.4.4 Design and construction of structural concrete 
slabs cast on stay-in-place, non-composite steel deck are 
governed by this chapter. 

401.4.5 Design and construction of one- and two- 
family dwellings and multiple single-family dwellings 
(townhouses) and their accessory structures may be 
designed until such time provisions of the National 
Structural Code of the Philippines, Volume III, Housing is 
published. 


National Structural Code of the Philippines Volume I, 7 th Edition, 2015 


4-8 CHAPTER 4 - Structural Concrete 


401.4.6 This chapter does not apply to the design and 
installation of concrete piles, drilled piers, and caissons 
embedded in ground except as provided in (a) or (b): 

a. For portions in air or water, or in soil incapable of 
providing adequate lateral restraint to prevent 
buckling throughout their length. See also Sect. 
418.13.1.2. 

b. For structures in region of high seismic risk or 
assigned to high seismic performance or design 
categories 

401.4.7 This chapter does not govern design and 
construction of slabs-on-ground, unless the slab transmits 
vertical loads or lateral forces from other portions of the 
structure to the soil. 

401.4.8 For unusual structures, such as arches, tanks, 
reservoirs, bins and silos, blast-resistant structures, and 
chimneys, provisions of this section shall govern where 
applicable. For tanks and reservoirs refer also to ACI 350, 
ACI 334. 1R, and ACI 372R. 

40L4.9 This chapter does not govern the composite 
design of structural concrete slabs cast-in-place, 
composite steel form deck. Concrete used in the 
construction of such slabs shall be governed by Sections 
401 to 406 of this chapter, where applicable. Portions of 
such slabs designed as reinforced concrete are governed 
by this chapter. 

401.5 Interpretation 

401.5.1 The principles of interpretation in this Section 
shall apply to this Chapter as a whole unless otherwise 
stated. 

401.5.2 This Chapter consists of sections and 
appendices, including text, headings, tables, figures, 
footnotes to tables and figures, and referenced standards. 

401.5.3 This Chapter shall be interpreted in a manner 
that avoids conflict between or among its provisions. 
Specific provisions shall govern over general provisions. 

401.5.4 This chapter shall be interpreted and applied in 
accordance with the plain meaning of the words and terms 
used. Specific definitions of words and terms in this 
section shall be used where provided and applicable, 
regardless of whether other materials, standards, or 
resources outside of this section provide a different 
definition. 


401.5.5 The following words and terms in this section 
shall be interpreted in accordance with (a) through (e): 

a. The word “shall” is always mandatory; 

b. Provisions of this section are mandatory even if the 
word “shall” is not used; 

c. Words used in the present tense shall include the 
future; 

d. The word “and” indicates that all of the connected 
items, conditions, requirements, or events shall apply; 

e. The word “or” indicates that all of the connected 
items, conditions, requirements, or events are 
alternatives, at least one of which shall be satisfied. 

401.5.6 In any case in which one or more provisions of 
this Chapter are declared by an appropriate court to be 
invalid, that ruling shall not affect the validity of the 
remaining provisions of this Chapter, which are severable. 
The ruling of the court shall be effective only in that 
court’s jurisdiction, and shall not affect the content of 
interpretation of this Chapter in other jurisdictions. 

401.5.7 If conflicts occur between provisions of this 
code and standards and documents referenced in Section 
403, this Chapter shall apply. 

401.6 Building Official 

401.6.1 All references in this chapter to the building 
official shall be understood to mean the persons who 
administer and enforce this Code. 

401.6.2 Actions and decisions by the building official 
affect only the specific jurisdiction and do not change this 
Code. 

401.6.3 The building official shall have the right to 
order testing of any materials used in concrete 
construction to determine if materials are of the quality 
specified. 

401.7 Licensed Design Professional 

401.7.1 All references in this Code to the licensed design 
professional shall be understood to mean the person who 
is licensed and responsible for, and in charge of, the 
structural design or inspection. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 4 - Structural Concrete 4-9 


401.8 Construction Documents and Design Records 

-401.8.1 The licensed design professional shall provide 
in the construction documents the information required in 
Section 426 and that required by the jurisdiction. 

401.8.2 Calculations pertinent lo design shall be filed 
with the construction documents if required by the 
building official. Analyses and designs using computer 
programs shall be permitted provided design assumptions, 
user input, and computer-generated output are submitted. 
Model analysis shall be permitted to supplement 
calculations. 

401.9 Testing and Inspection 

401.9.1 Concrete materials shall be tested in 
accordance with the requirements of Section 426. 

401.9.2 Concrete construction shall be inspected in 
accordance with the general building code and in 
accordance with Sections 417 and 426. 

401.9.3 Inspection records shall include information 
required in Sections 417 and 426. 

401.10 Approval of Special Systems of Design, 
Construction, or Alternative Construction 
Materials 

401.10.1 Sponsors of any system of design, 
construction, or alternative construction materials within 
the scope oi this Chapter, the adequacy of which has been 
shown by successful use or by analysis or test, but which 
does not conform to or is not covered by this Chapter, 
shall have the right lo present the data on which their 
design is based to the building official or to a committee 
of competent structural engineers appointed by the 
building official. This committee shall have the authority 
to investigate the data so submitted, require tests, and 
formulate rules governing design and construction of such 
systems to meet the intent of this Code. These rules, when 
approved by the building official, and promulgated, shall 
be of the same force and effect as the provisions of this 
Code. 

401.11 Provisions for Earthquake Resistance 

401.11.1 In regions of moderate (seismic zone 2) or 
high seismic risk (seismic zone 4), provisions of Section 
418 shall be satisfied. 


SECTION 402 

NOTATION AND TERMINOLOGY 

402.1 Scope 

402.1.1 This section defines notation and terminology 

used in this chapter. 

402.2 Notation 

a = shear span, distance between 

concentrated load and face of 
supports, mm. 

a = depth of equivalent rectangular stress 

block, mm. 

ttp — shear span, equal to distance from 

center of concentrated load to either: 
(a) face of support for continuous or 
cantilevered members, or (b) center 
of support for simply supported 
members, mm. 

A = area of that part of cross section 

between flexural tension face and 
center of gravity of gross section, 
mm 2 . 

Ab = Area of an individual bar or wire, 

mm 2 . 

A brg = net bearing area of the head of stud, 

anchor bolt, or headed deformed bar c 

2 

mm. 

A c ~ area of concrete section resisting 

shear transfer, mm 2 . 

= area of contact surface being 

investigated for horizontal shear, 

2 

mm . 

A C f = greater gross cross-sectional area of 

the slab-beam strips of the two 
orthogonal equivalent frames 
intersecting at a column of a two-way 
slab, mm 2 . 

A c h = cross-sectional area of a member 

measured to the outside edges of 
transverse reinforcement, mm 2 . 

Acp = area enclosed by outside perimeter of 

concrete cross section, mm 2 . 

A C s = cross-sectional area at one end of a 

strut in a strut-and-tie model, taken 
perpendicular to the axis of the strut, 
mm 2 

A c t = area of that part of cross section 

between the flexural tension face and 
centroid of gross section, mm 2 


National Structural Code of the Philippines Volume f 7 th Edition, 2015 


4-1 0 CHAPTER 4 - Structural Concrete 


= gross area of concrete section 
bounded by web thickness and length 
of section in the direction of shear 
force considered in the case of walls, 
and gross area of concrete section in 
the case of diaphragms, not to exceed 
the thickness times the width of the 
diaphragm, mm 2 . 

A cw = area 0 f concrete section of an 

individual pier, horizontal wall 
segment, or coupling beam resisting 
shear, mm 2 . 

Af = area of reinforcement in bracket or 

corbel resisting design moment, mm 2 

A g = gross area of concrete section, mm . 

For a hollow section, A g is the area 
of the concrete only and does not 
include the area of the void(s). 

A h = total area of shear reinforcement 

parallel to primary tension 
reinforcement in a corbel or bracket, 
mm 2 . 

Aj = effective cross-sectional area within a 

joint in a plane parallel to plane of 
beam reinforcement generating shear 
in the joint, mm 2 . 

A t = total area of longitudinal 

reinforcement to resist torsion, mm . 

A = minimum area of longitudinal 

reinforcement to resist torsion, mm . 

A n = area of reinforcement in bracket or 

corbel resisting factored tensile force 
Nuc> mm 2 . 

A nz = area of a face of a nodal zone or a 

section through a nodal zone, mm 2 . 

A Na = projected influence area of a single 

adhesive anchor or group of adhesive 
anchors, for calculation of bond 
strength intension, mm 2 . 

A Nao = P r °j ecte( i influence area of a single 

adhesive anchor, for calculation of 
bond strength in tension if not limited 
by edge distance or spacing, mm 2 . 

A Nc = projected concrete failure area of a 

single anchor or group of anchors, 
for calculation of strength in tension, 
mm 2 . 

An co = projected concrete failure area of a 

single anchor, for calculation of 
strength intension if not limited by 
edge distance or spacing, mm 2 . 

A 0 = gross area enclosed by torsional shear 

flow path, mm 2 . 


A oh = area enclosed by centerline of the 

outermost closed transverse torsional 
reinforcement, mm 2 . 

A p d = tot£ d area occupied by duct, 

sheathing, and prestressing 
reinforcement, mm 2 . 

A ps = area of prestressed reinforcement in 

tension zone, mm 2 . 

A p t = total area of prestressing 

reinforcement, mm 2 . 

A s - area of non-prestressed longitudinal 

tension reinforcement, mm 2 . 

A! = area of compression reinforcement, 

s 2 
mm . 

A sc = area of primary tension 

reinforcement in a corbel or bracket, 
mm 2 . 

A S eN = effective cross-sectional area of 

anchor intension, mm 2 . 

A „ = effective cross-sectional area of 

n se,V 2 

anchor in shear, mm . 

A S h = tota l cross-sectional area of 

transverse reinforcement, including 
crossties, within spacing s and 

perpendicular to dimension b c , mm 2 . 

A si = total area of surface reinforcement at 

spacing s t in the i-th layer crossing a 
strut, with reinforcement at an angle 
a t to the axis of the strut, mm 2 . 

A s min = minimum area of flexural 
reinforcement, mm 2 . 

A st = total area of non-prestressed 

longitudinal reinforcement bars or 
sfeel shapes, and excluding 
prestressing reinforcement, mm . 

A sx = area stee * s h a P e > piP e > or tu ^i n 8 m 

a composite section, mm 2 . 

A t = area of structural steel shape, pipe or 

tubing in a composite section, mm . 

A t = total area of longitudinal 

reinforcement to resist torsion, mm . 

A tp = area of prestressing reinforcement in 

a tie, mm 2 . 

A tr = total cross-sectional area of all 

transverse reinforcement within 
spacing s that crosses the potential 
plane of splitting through the 
reinforcement being developed, 
mm 2 . 

A ts = area of non-prestressed reinforcement 

in a tie, mm. 

A v = area of shear reinforcement within 

spacing s, mm 2 . 

A vd = total area of reinforcement in each 

group of diagonal bars in a 
diagonally reinforced coupling beam, 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 4 - Structural Concrete 


4-1 1 


mm 2 . 

area of shear friction reinforcement, 
mm 2 . 

area of shear reinforcement parallel 
to flexural tension reinforcement 
within spacing s 2 , mm 2 , 
minimum area of shear reinforcement 
within spacing s , mm 2 , 
projected concrete failure area of a 
single anchor or group of anchors, for 
calculation of strength in shear, mm 2 , 
projected concrete failure area of a 
single anchor, for calculation of 
strength in shear, if not limited by 
comer influences, spacing, or 
member thickness, mm 2 , 
loaded area for consideration of 
bearing strength, mm 2 , 
maximum area of the portion of the 
supporting surface that is 
geometrically similar to and 
concentric with the loaded area, 
the area of the lower base of the 
largest frustum of a pyramid, cone, or 
tapered wedge contained wholly 
within the support and having its 
upper base equal to the loaded area. 
The sides of the pyramid, cone, or 
tapered wedge shall be sloped one 
vertical to two horizontal, mm 2 , 
width of compression face of 
member, mm. 

cross-sectional dimension of member 
core measured to the outside edges of 
the transverse reinforcement 
composing area A sh , mm. 

Effective flange width of T section, 
mm. 

perimeter of critical section for two- 

way shear in slabs and footings, mm. 

width of a strut, mm. 

the effective slab width resisting 

Y f M sc . 

width of that part of cross section 

containing the closed stirrups 

resisting torsion, mm. 

width of cross section at contact 

surface being investigated for 

horizontal shear, mm. 

web width or diameter of circular 

section, mm. 

dimension of the critical section b 0 
measured in the direction of the span 
for which moments are determined, 
mm. 

dimension of the critical section b 0 


measured in the direction 
perpendicular to b x , mm. 

B n = nominal bearing strength, N. 

B u = factored bearing load, N. 

c — distance from extreme compression 

fiber to neutral axis, mm. 

c ac = critical edge distance required to 

develop the basic strength as 
controlled by concrete breakout or 
bond of a post-installed anchor in 
tension in uncracked concrete 
without supplementary reinforcement 
to control splitting, mm. 

c a,max = maximum distance from center of an 
anchor shaft to the edge of concrete, 
mm. 

c a,min = minimum distance from center of an 

anchor shaft to the edge of concrete, 
mm. 

c al = distance from the center of an anchor 

shaft to the edge of concrete in one 
direction, mm. If shear is applied to 
anchor, c al is taken in the direction 
of the applied shear. If tension is 
applied to the anchor, c al is the 
minimum edge distance. Where 
anchors subject to shear are located 
in narrow sections of limited 
thickness, See Section 417.5.2.4. 

c' al = limiting value of c al where anchors 

are located less than 1.5c al from 
three or more edges, mm. 

c a2 = distance from center of an anchor 

'shaft to the edge of concrete in the 
direction perpendicular to c al , mm. 

c b = lesser of: (a) the distance from center 

of a bar or wire to the nearest 
concrete surface, and (b) one-half the 
center-to-center spacing of bars or 
wires being developed, mm. 

c c = clear cover of reinforcement, mm. 

c Na = projected distance from center of an 

anchor shaft on one side of the 
anchor required to develop the full 
bond strength of a single adhesive 
anchor, mm. 

c t = distance from the interior face of the 

column to the slab edge measured 
parallel to c 1? but not exceeding c 1? 
mm. 

c x = dimension of rectangular or 

equivalent rectangular column, 

capital, or bracket measured in the 
direction of the span for which 
moments are being determined, mm. 

c 2 = dimension of rectangular or 


National Structural Code of the Philippines Voiume I, 7 th Edition, 2015 


4-12 CHAPTER 4- Structural Concrete 


equivalent rectangular column, 
capital, or bracket measured in the 
direction perpendicular to c l5 mm. 

C = cross-sectional constant to define 

torsional properties of slab and beam. 
= compressive force acting on a nodal 
zone, N. 

C m = a factor relating actual moment 

diagram to an equivalent uniform 
moment diagram. 

d = distance from extreme compression 

fiber to centroid of longitudinal 
tension reinforcement, mm. 

d ' = distance from extreme compression 

fiber to centroid of longitudinal 
compression reinforcement, mm. 

d a = outside diameter of anchor or shaft 

diameter of headed stud, headed bolt, 
or hooked bolt, mm. 

d! a = value substituted for d a if an 

oversized anchor is used, mm. 

d a gg = Nominal maximum size of coarse 

aggregate, mm. 

d b = nominal diameter of bar, wire, or 

prestressing strand, mm. 

d p = distance from extreme compression 

fiber to centroid of prestressed 
reinforcement, mm. 

dp He = diameter of pile at footing base, mm. 

d s distance from extreme tension fiber 

to centroid of tension reinforcement, 
mm. 

D = dead loads or related internal 

moments and forces. 

D = effect of service dead load. 

e h = distance from the inner surface of the 

shaft of a J- or L-bolt to the outer tip 
of the J- or L-bolt, mm. 

e N r distance between resultant tension 

load on a group of anchors loaded in 
tension and the centroid of the group 
of anchors loaded in tension, mm; 
e N t is always positive. 

e v t = distance between resultant shear load 

on a group of anchors loaded in shear 
in the same direction, and the 
centroid of the group of anchors 
loaded in shear in the same direction, 
mm; e v r is always positive. 


E 

= effect of horizontal and 
earthquake-induced forces. 

vertical 

E c 

= modulus of elasticity of 
MPa. 

concrete, 

Ecb 

= modulus of elasticity of beam 
concrete, MPa. 

Ecs 

= modulus of elasticity 

of slab 


El 

(£/)*,/ 

E p 

E s 


f'c 

4Tc 

fee 

fei’ 


f cm 
fet 
fa 


fdc 


fpc 


fpe 


fps 


concrete, MPa. 

= flexural stiffness of member, N-mm 2 . 

= Effective flexural stiffness of 

member, N-mm 2 . 

= modulus of elasticity of prestressing 
reinforcement, MPa. 

= modulus of elasticity of 
reinforcement and structural steel, 
excluding prestressing reinforcement, 
MPa. 

= specified compressive strength of 
concrete, MPa. 

= square root of specified compressive 
strength of concrete, MPa. 

= effective compressive strength of the 
concrete in a strut or a nodal zone, 
MPa. 

= compressive strength of concrete at 
time of initial prestress, MPa. 

= square root of specified compressive 
strength of concrete at time of initial 
prestress, MPa. 

= measured average compressive 
strength of concrete, MPa. 

= average splitting tensile strength of 
lightweight concrete, MPa. 

= stress due to unfactored dead load, at 
extreme fiber of section where tensile 
stress is caused by externally applied 
loads, MPa. 

= decompression stress; stress in the 
prestressing steel when stress is zero 
in the concrete at the same level as 
the centroid of the prestressing steel, 
MPa. 

= compressive stress in concrete, after 
allowance for all prestress losses, at 
centroid of cross section resisting 
externally applied loads or at junction 
of web and flange where the centroid 
lies within the flange, MPa. In a 
composite member, f pc is resultant 
compressive stress at centroid of 
composite section, or at junction of 
web and flange where the centroid 
lies within the flange, due to both 
prestress and moments resisted by 
precast member acting alone. 

= compressive stress in concrete due to 
effective prestress forces, after 
allowance for all prestress losses, at 
extreme fiber of section if tensile 
stress is caused by externally applied 
loads, MPa. 

= stress in prestressing steel at nominal 
flexural strength, MPa. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


*n *»i 


CHAPTER 4 - Structural Concrete 4-13 



/pu 

= specified tensile strength 
prestressing reinforcement, MPa, 

of 

/ 

f py 

= specified yield strength 

prestressing reinforcement, MPa. 

of 


fr 

- modulus of rupture of concrete, MPa. 


fs 

- tensile stress in reinforcement 

at 


service loads, excluding prestressing 
reinforcement, MPa. 

f s = compressive stress in reinforcement 

under factored loads, excluding 
prestressing reinforcement, MPa. 

f se = effective stress in prestressed 

reinforcement (after allowance for all 
prestress losses), MPa. 

f si = stress in the Ath layer of surface 

reinforcement MPa. 

ft = extreme fiber stress in tension in the 

pre-compressed tensile zone 
calculated at service loads using 
gross section properties after 
allowance of all prestress losses, 
MPa. 

futa = specified tensile strength of anchor 

steel, MPa. 

f y = specified yield strength of non- 

prestressed reinforcement, MPa. 

fya = specified yield strength of anchor 

steel, MPa. 

f yt = specified yield strength of transverse 

reinforcement, MPa. 

F = effect of service lateral load due to 

fluids with well-defined pressures 
and maximum heights. 

F nn = nominal strength at face of a nodal 

zone, N. 

= nominal strength of a strut, N. 

= nominal strength of a tie, N. 

= factored force on the face of a node, 
N. 

F us = factored compressive force in a strut, 

N. 

F ut = factored tensile force in a tie, N. 

h = overall thickness of member, mm. 

h = thickness of shell or folded plate, 

mm. 

h a = thickness of member in which an 

anchor is located, measured parallel 
to anchor axis, mm. 

h>anc = dimension of anchorage device or 

single group of closely spaced 
devices in the direction of bursting 
being considered, mm. 

h e f = effective embedment depth of anchor, 

mm. 

h' e f = limiting value of h e f where anchors 

are located less than l.Sh e f from 


three or more edges, mm. 
h sx = storey height for storey x, 

h u = laterally unsupported height at 

extreme compression of wall or wall 
pier, mm., equivalent to F u for 
compression members, mm. 
h v = depth of shear head cross section, 


K 

h x 

H 


I 


h 


Is 

/* 


k 

k c 

k C p 

k f 

k, n 

K 

K t 

K tr 

*05 

€ 

*a 


= height of entire wall from base to top, 
or clear height of wall segment or 
wall pier considered, mm. 

= maximum center to center horizontal 
spacing of hoop or crosstie legs on all 
faces of the column, mm. 

= effect of service load due to lateral 
earth pressure, ground water 
pressure, or pressure of bulk 
materials, N. 

= moment of inertia of section of beam 
about the centroidal axis, mm 4 . 

= moment of inertia about centroidal 
axis of gross section of beam, mm 4 . 

= moment of inertia of cracked section 
transformed to concrete, mm 4 . 

= effective moment of inertia for 
computation of deflection, mm 4 . 

= moment of inertia of gross concrete 
section about centroidal axis, 
neglecting reinforcement, mm 4 . 

= moment of inertia about of slab about 
centroidal axis, mm 4 . 

= moment of inertia of reinforcement 
about centroidal axis of member 
- cross section, mm 4 . 

= moment of inertia of structural steel 
shape, pipe or tubing about centroidal 
axis of composite member cross 
section, mm 4 . 

= effective length factor for 
compression members. 

= coefficient for basic concrete 
breakout strength in tension. 

= coefficient for pry out strength. 

= concrete strength factor. 

= confinement effectiveness factor. 

= wobble friction coefficient per mm of 
prestressing tendon. 

= torsional stiffness of torsional 
member; moment per unit rotation. 

= transverse reinforcement index, mm. 

= coefficient associated with the 5% 
fractile. 

= span length of beam or one-way slab; 

clear projection of cantilever, mm. 

= additional embedment length beyond 
centerline of support or point of 


National Structural Code of the Philippines Volume ! : 7 th Edition, 2015 


4-14 CHAPTER 4 - Structural Concrete 


inflection, mm. 

£ = length along which anchorage of a tie 

must occur, mm. 

£ b = width of bearing, mm. 

£ c = length of a compression member in a 

frame, measured center-to-center of 
the joints, mm. 

£ d = development length in tension of 

deformed bar, deformed wire, plain 
and deformed welded wire 
reinforcement, or pretensioned 
strand, mm. 

£ dc = development length in compression 

of deformed bars and deformed wire, 
mm. 

£ dh = development length in tension of 

deformed bar or deformed wire with 
a standard hook, measured from 
outside end of hook, point of 

tangency, toward critical section, 
mm. 

£ e = load bearing length of anchor for 

shear, mm. 

£ n = length of clear span measured face- 

to-face of supports, mm. 

£ o = length, measured from joint face 

along axis of member, over which 
special transverse reinforcement must 
be provided, mm. 

£ sc = compression lap splice length, mm. 

£ st = tension lap splice length, mm. 

£ t = span of member under load test, 

taken as the shorter span for two-way 
slab systems, mm. Span is the lesser 
of: (a) distance between centers of 
supports, and (b) clear distance 
between supports plus thickness h of 
member. Span for a cantilever shall 
be taken as twice the distance from 
the face of support to cantilever end. 

£ tr = transfer length of prestressed 

reinforcement, mm. 

£ u = unsupported length of column or 

wall, mm 

£ v = length of shear head arm from 

centroid of concentrated load or 
reaction, mm. 

£ w = length of entire wall, or length of 

wall segment or wall pier considered 
in direction of shear force, mm. 

£ x = length of prestressing tendon element 

from jacking end to any point x , mm. 

£ 1 = length of span in direction that 

moments are being determined, 
measured center-to-center of 
supports, mm. 


£ 2 = length of span in direction 

perpendicular to £ l9 measured center- 
to-center of supports, mm. 

L = effect of service live load. 

l d = development length, mm. 

I = effect of service roof live load. 

M = design moment 

= maximum unfactored moment due to 
service loads, including effects. 

yif = moment acting on anchor or anchor 

group, N-mm. 

M a = maximum moment in member due to 

service loads at stage deflection is 
calculated, N-mm. 

M c = moment at the face of the joint, 

corresponding to the nominal flexural 
strength of the column framing into 
that joint, calculated for the factored 
axial force, consistent with the 
direction of the lateral forces 
considered, resulting in the lowest 
flexural strength. 

M c = factored moment amplified for the 

effects of member curvature used for 
design of compression member, N- 
mm. 

M cr = cracking moment, N-mm. 

M cre = moment causing flexural cracking at 

section due to externally applied 
loads, N-mm 

M g - moment at the face of the joint, 

corresponding to the nominal flexural 
strength of the girder including slab 
where in tension, framing into that 
joint 

M = factored moment modified to account 

111 XT 

for effect of axial compression, N- 
mm. 

M max = maximum factored moment at section 
due to externally applied loads, N- 
mm. 

M n = nominal flexural strength at section, 

N-mm. 

M nb = nominal flexural strength of beam 

including slab where in tension, 
framing into joint, N-mm. 

M nc = nominal flexural strength of column 

framing into j oint, calculated for 
factored axial force, consistent with 
the direction of lateral forces 
considered, resulting in lowest 
flexural strength, N-mm. 

M 0 = total factored static moment, N-mm. 

M p = required plastic moment strength of 

shearhead cross section, N-mm. 

M pr = probable flexural strength of 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


members, with or without axial load, 
determined using the properties of the 
member at the joint faces assuming a 

n 

- modular ratio of elasticity, but not 
less than 6 

= e s /e c 

tensile strength in the longitudinal 
bars of at least 1.25 f y and a 
strength-reduction factor (f> of 1.0, N- 

n 

= number of items, such as, bars, wires, 
monostrand anchorage devices, 
anchors or shearhead arms. 

mm. 

maximum moment in wall due to 
service loads, excluding P A effects, 
N-mm. 

factored slab moment that is resisted 
by the column at a joint, N-mm. 

n, 

= number of longitudinal bars around 
the perimeter of a column core with 
rectilinear hoops that are laterally 
supported by the corner of hoops or 
by seismic hooks. A bundle of bars 
is counted as a single bar. 

portion of slab factored moment 
balanced by support moment, N-mm 
factored moment at section, N-mm. 
moment at the mid-height section of 
the wall due to factored lateral and 
eccentric vertical loads, not including 

P A effects, N-mm. 

moment resistance contributed by 
shearhead reinforcement, N-mm. 

N 

= design axial load normal to cross 
section occurring simultaneously 
with V; to be taken as positive for 
compression, negative for tension, 
and to include effects of tension due 
to creep and shrinkage. 

= number of bars in a layer being 
spliced or developed at a critical 
section. 

lesser factored end moment on a 
compression member, to be taken as 

N 

= tension force acting on anchor or 
anchor group, N. 

positive if member is bent in single 
curvature, negative if bent in double 

N a 

= nominal bond strength intension of a 
single adhesive anchor, N. 

curvature, N-mm. 

factored end moment on a 

N ag 

= nominal bond strength intension of a 
group of adhesive anchors, N. 

compression member at the end at 
which M 1 acts, due to loads that 
cause no appreciable sidesway, 

N b 

= basic concrete breakout strength in 
tension of a single anchor in cracked 
concrete, N. 

calculated using a first-order elastic 
frame analysis, N-mm. 

N ba 

= Basic bond strength in tension of a 
single adhesive anchor, N. 

factored end moment on compression 
member at the end at which M x acts, 
due to loads that cause appreciable 
sidesway, calculated using a first- 
order elastic frame analysis, N-mm. 
greater factored end moment on 

N c 

= the resultant tensile force acting on 
the portion of the concrete cross 
section that is subjected to tensile 
stresses due to the combined effects 
of service loads and effective 
prestress, N. 

compression member. If transverse 
loading occurs between supports, 

N cb 

= nominal concrete breakout strength in 
tension of a single anchor, N. 

M 2 is taken as the largest moment 
occurring in member. Value of M 2 

N cb g 

= nominal concrete breakout strength in 
tension of a group of anchors, N, 

is always positive, N-mm. 
minimum value of ilf 2 , N-mm. 

N cp 

= basic concrete pryout strength of a 
single anchor, N. 

factored end moment on compression 
member at the end at which M 2 acts. 

N C pg 

= basic concrete pryout strength of a 
group of anchors, N. 

due to loads that cause no appreciable 

Nn 

= nominal strength in tension, N. 

sidesway, calculated using a first- 
order elastic frame analysis, N-mm. 

N v 

= pullout strength in tension of a single 
anchor in cracked concrete, N. 

factored end moment on compression 
member at the end at which M 2 acts, 

N pn 

= nominal pullout strength in tension of 
a single anchor, N 

due to loads that cause appreciable 
sidesway, calculated using a first- 
order elastic frame analysis, N-mm. 

N sa 

= nominal strength of a single anchor 
or individual anchors in a group of 
anchors in tension as governed by the 
steel strength, N. 


4-1 6 CHAPTER 4 - Structural Concrete 


N sb 

N sbg 

N u 


N u a 

^ua, g 

Nua,i 


N 


ua,s 

N„ r 


Pep 

Ph 


Pc 

Pn 

,max 

Pnt 

J 

nt, max 

Po 

Ppi 

P pu 
Ppx 

Ps 

Pn 


= side-face blowout strength of a single 
anchor, N. 

= side-face blowout strength of a group 
of anchors, N. 

= factored axial force normal to cross 
section occurring simultaneously 
with V u or T u \ to be taken as 
positive for compression and 
negative for tension, N. 

= factored tensile force applied to 
anchor or individual anchor in a 
group of anchors, N. 

= total factored tensile force applied to 
anchor group, N. 

= factored tensile force applied to most 
highly stressed anchor in a group of 
anchors, N. 

= . Factored sustained tension load, N. 

= factored horizontal tensile force 
applied at top of bracket or corbel 
acting simultaneously with V u ; to be 
taken as positive for tension, N. 

= outside perimeter of the concrete 
cross section, mm. 

= perimeter of centerline of outermost 
closed transverse torsional 
reinforcement, mm. 

= critical buckling load, N. 

= nominal axial compressive strength 
of a member, N. 

= maximum nominal axial compressive 
strength of member, N. 

= nominal axial tensile strength of 
member, N. 

= Maximum nominal axial tensile 
strength of member, N. 

= nominal axial load strength at zero 
eccentricity, N. 

= prestressing force at jacking end, N. 

= factored prestressing force at 
anchorage device, N. 

= prestressing force evaluated at 
distance £ px from the jacking end, N 
= prestressing tendon force at jacking 
end. 

= unfactored axial load at the design, 
mid-height section including effects 
of self-weight, N. 

= factored post-tensioned tendon force 
at the anchorage device. 

= factored axial load at given 
eccentricity, < 4>Pn 

= Factored axial force; to be taken as 
positive for compression and 
negative for tension, N. 


PS 

PA 

P x 


Qdu 

Rlu 

Qu 

Q 

r 

R 

R 

s 


s 


s 


Si 


So 


S s 

s w 

s w 

S 2 


S 

S e 


Sy 

t 

tf 


= secondary moment due to individual 
member slenderness, N-mm. 

= secondary moment due to lateral 
deflection, N-mm. 

= prestressing tendon force at any point 
x . 

= factored dead load per unit area, kPa. 

= factored live load per unit area, kPa. 

= factored load per unit area, kPa. 

= stability index for a storey. 

= radius of gyration of cross section of 
a compression member, mm. 

= reaction, N. 

= cumulative load effect of service rain 
load. 

= spacing of shear reinforcement in 
direction parallel to longitudinal 
reinforcement, mm. 

= center-to-center spacing of items, 
such as longitudinal reinforcement, 
transverse reinforcement, tendons, or 
anchors, mm. 

= Standard deviation, MPa. 

= center-to-center spacing of 
reinforcements in the i-th layer 
adjacent to the surface of the 
member, mm. 

= center-to-center spacing of transverse 
reinforcements within the length 
f 0 , mm. 

= sample standard deviation, MPa. 

= spacing of wire to be developed or 
spliced, mm. 

= clear distance between adjacent webs, 
mm. 

= center-to-center spacing of 
longitudinal shear or torsional 
reinforcement, mm. 

= elastic section modulus of section. 

= moment, shear or axial force at 
connection corresponding to 

development of probable strength at 
intended yield locations, based on the 
governing mechanism of inelastic 
lateral deformation, considering both 
gravity and earthquake load effects. 

= elastic section modulus, mm 3 . 

= nominal moment, shear, axial, 
torsional, or bearing strength. 

= yield strength of connection, based 
on / y , for moment, shear, of axial 
force, MPa. 

= wall thickness of hollow section, mm. 
= thickness of flange, mm. 


Association of Structural Engineers of the Philippines ! Inc. (ASEP) 


CHAPTER 4 - Structural Concrete 4-1 7 


cumulative effects of service 
temperature, creep, shrinkage, 
differential settlement, and shrinkage 
compensating concrete, 
tension force acting on a nodal zone 
in a strut-and-tie model, N. 
cracking torsional moment, N-mm. 
total test load, N. 

threshold torsional moment, N-mm. 
factored torsional moment at section, 
N-mm. 

strength of a member or cross section 
required to resist factored loads or 
related internal moments and forces 
in such combinations as stipulated in 
this Code. 

design shear stress, MPa, 

Stress corresponding to nominal two- 
way shear strength provided by 
concrete, MPa. 

equivalent concrete stress 
corresponding to nominal two-way 
shear strength of slab or footing, 
MPa. 

equivalent concrete stress 
corresponding to nominal two-way 
shear strength provided by 
reinforcement, MPa. 

Maximum factored two-way shear 
stress calculated around the perimeter 
of a given critical section, MPa. 
factored shear stress on the slab 
critical section for two-way action 
due to gravity loads without moment 
transfer, MPa. 

design shear force at section 

shear force acting on anchor or 

anchor group, N. 

applied shear perpendicular to the 
edge, N. 

applied shear parallel to the edge, N. 
basic concrete breakout strength in 
shear of a single anchor in cracked 
concrete, N. 

nominal shear strength provided by 
concrete, N. 

nominal concrete breakout strength in 
shear of a single anchor, N. 
nominal concrete breakout strength in 
shear of a group of anchors, N. 
nominal shear strength provided by 
concrete where diagonal cracking 
results from combined shear and 
moment, N. 

nominal concrete pryout strength of a 
single anchor, N. 


v 

v cpg 

u 

v cw 


V d 

V e 

v h 

V, 


V n 

Vnh 

V P 

V s 



v 

v ua,g 

V 

v ua,i 


v uh 


V 


US 




W t 

Wu 

Ws 

W t 


Wt,max 

w/cm 

W 

W a 


= nominal concrete pryout strength of a 
group of anchors, N. 

= nominal shear strength provided by 
concrete where diagonal cracking 
results from high principal tensile 
stress in web, N. 

= shear force at section due to 
unfactored dead load, N. 

= Design shear force for load 
combinations including earthquake 
effects, N. 

= permissible horizontal shear stress, 
MPa. 

= factored shear force at section due to 
externally applied loads occurring 
simultaneously with M max , N. 

= nominal shear strength, N. 

= nominal horizontal shear strength, N. 
= vertical component of effective 
prestress force at section, N. 

= nominal shear strength provided by 
shear reinforcement, N. 

= nominal strength in shear of a single 
anchor or group of anchors as 
governed by the steel strength, N. 

= factored shear force at section, N. 

= factored shear force applied to a 
single anchor or group of anchors, N. 
= total factored shear force applied to 
anchor group, N. 

= factored shear force applied to most 
highly stressed anchor in a group of 
anchors, N. 

= Factored shear force along horizontal 
interface in composite concrete 
flexural member, N. 

= factored horizontal shear in a storey, 
N. 

= density, unit weight, of normal- 
weight concrete or equilibrium 
density of lightweight concrete, kg/ 
m 3 . 

= factored live load per unit area. 

= factored load per unit length of beam 
or one-way slab, N/mm. 

= width of a strut perpendicular to the 
axis of the strut, mm. 

= effective height of concrete 
concentric with a tie, used to 
dimension nodal zone, mm. 

= maximum effective height of 
concrete concentric with a tie, mm. 

= maximum water-cementitious 
materials ratio. 

= effect of wind load. 

= service-level wind load, N. 


National Structural Code of the Philippines Volume I, 7 th Edition, 2015 


4-18 CHAPTER 4 - Structural Concrete 


X 

= shorter overall dimension of 

Pds 

— 

y 

7t 

rectangular part of cross section, mm. 

= longer overall dimension of 

rectangular part of cross section, mm. 

= distance from centroidal axis of gross 
section, neglecting reinforcement, to 

Pdns 


a 

tension face, mm. 

= angle between inclined stirrups and 
longitudinal axis of member. 

Pn 

= 

a 

a 

= angle defining the orientation of 
reinforcement. 

= total angular change of prestressing 
tendon profile in radians from tendon 

Ps 



«c 

a f 

jacking end to any point x . 

= coefficient defining the relative 
contribution of concrete strength to 
nominal wall shear strength 
= ratio of flexural stiffness of beam 

Pt 


T 

section to flexural stiffness of a width 
of slab bounded laterally by 
centerlines of adjacent panels, if any, 
on each side of the beam. 

Pt 


a f 

Ecb^b 

F I 

1j cs 1 s 

Pi 

= 

Ctfm 

= average value of af for all beams 
on edges of a panel. 

Vt 



af 1 = ctf in direction of 


- af in direction of 



= angle between the axis of a strut and 

Yp 

— 


the bars in the i-th layer of 
reinforcement crossing that strut. 


Yp 

a 

= total angular change of tendon profile 

— 


from tendon jacking end to point 
under considerations, radians. 


= 

a s 

= constant used to compute V c in slabs 

Ys 



and footings. 



a» 

= ratio of flexural stiffness of shear 




head arm to surrounding composite 
slab section. 

Yv 


« 1 

= orientation of distributed 

Yv 


reinforcement in a strut. 


«2 

= orientation of reinforcement 

5 

= 

orthogonal to a x in a strut. 

= ratio of long to short dimensions: 



P 

clear span for two-way slabs, sides of 
column, concentrated load or reaction 

8s 

= 


Pb 

area; or sides of a footing. 

= ratio of area of reinforcement cut off 



to total area of tension reinforcement 
at section. 

8 U 



Pc 

= ratio of long side to short side of 

A cr 

= 


concentrated load or reaction area 

^fmax 

= 


the ratio of maximum factored 
sustained shear within a storey to the 
maximum factored shear in that 
storey associated with the same load 
combination. 

ratio used to account for reduction of 
stiffness of columns due to sustained 
axial loads. 

factor used to account for the effect 
of the anchorage of ties on the 
effective compressive strength of a 
nodal zone. 

factor used to account for the effect 
of cracking and confining 
reinforcement on the effective 
compressive strength of the concrete 
in a strut. 

ratio of torsional stiffness of edge 
beam section to flexural stiffness of a 
width of slab equal to span length of 
beam, center-to-center of supports. 

2 Ecs^s 

factor relating depth of equivalent 

rectangular compressive stress block 

to depth of neutral axis. 

factor used to determine the fraction 

of M sc transferred by slab flexure at 

slab-column connections. 

factor for type of prestressing 

reinforcement. 

0.55 for fpy/fpu not less than 0.80. 
0.40 for f P y/f P u not less than °* 85 ’ 
0.28 for fpy/fpu not less than 0.90. 
factor used to determine the portion 
of reinforcement located in center 
band of footing. 

factor used to determine the fraction 
of M sc transferred by eccentricity of 
shear at slab-column connections. 

1 - 7 / 

: Moment magnification factor used to 
reflect effects of member curvature 
between ends of compression 
member. 

= moment magnification factor for 
frames not braced against sideways, 
to reflect lateral drift resulting from 
lateral and gravity loads. 

= design displacement, mm. 

= computed, out-of-plane deflection at 
mid-height of wall corresponding to 
cracking moment, Af cr , mm. 

= maximum deflection measured 
during the second test relative to the 


Association of Structural Engineers of the Philippines, Inc* (ASEP) 


position of the structure at the 
beginning of the second test, mm. 

Af p = increase in stress i n prestressing 

reinforcement due to factored loads, 
MPa. 

Afp S = stress in prestressing reinforcement at 

service loads less decompression 
stress, MPa. 

Afpt = difference between the stress that can 

be developed in the strand at the 
section under consideration and the 
stress required to resist factored 
bending moment at section, M u /0, 
MPa. 

A max = measured maximum deflection, mm. 

A n = calculated, out-of-plane deflection at 

mid-height of wall corresponding to 
nominal flexural strength, Af n , mm. 

A 0 = relative lateral deflection between the 

top and bottom of a storey due to 
V us , mm. 

A r = residual deflection measured 24 hours 

after removal of the test load. For the 
first load test, residual deflection is 
measured relative to the position' of 
the structure at the beginning of the 
first load test. For the second load 
test, residual deflection is measured 
relative to the position of the 
structure at the beginning of the 
second load test, mm. 

A rmax = measured residual deflection, mm. 

A s = maximum deflection at or near 

midheight due to service loads, mm 

A s = out-of-plane deflection due to service 

loads, mm. 

A u = calculated out-of-plane deflection at 

mid-height of wall due to factored 
loads, mm. 

A* = design storey drift of storey x , mm, 

A ± = maximum deflection, during first 

load test, measured 24 hours after 
application of the full test load, mm. 

A 2 = maximum deflection, during second 

load test, measured 24hours after 
application of the full test load. 
Deflection is measured relative to the 
position of the structure at the 
beginning of second load test, mm. 

£ cu = maximum usable strain at extreme 

concrete compression fiber. 

£ t = net tensile strain in extreme layer of 

longitudinal tension reinforcement at 
nominal strength, excluding strains 
due to effective prestress, creep, 
shrinkage, and temperature. 


£ ty 


e 


x 

X 


K 


X , a 

ft 

V 

ftp 

f 

P 

P 

P 

p' 

Pb 

Pi 


Pp 


Ps 


Pt 


Pv 

Pv 

Pw 

<t> 


= value of net tensile strain in the 
extreme layer of longitudinal tension 
reinforcement used to define a 
compression-controlled section. 

= angle between axis of stmt, 
compression diagonal, or 
compression field and the tension 
chord of the members. 

= correction factor related to unit 
weight of concrete. 

= modification factor to reflect the 
reduced mechanical properties of 
lightweight concrete relative to 
normal-weight concrete of the same 
compressive strength. 

= modification factor to reflect the 
reduced mechanical properties of 
lightweight concrete in certain 
concrete anchorage applications. 

= multiplier used for additional 
deflection due to long-term effects. 

= coefficient of friction. 

= number of identical arms of 
shearhead. 

= post-tensioning curvature friction 
coefficient. 

= time-dependent factor for sustained 
load. 

= ratio of non-prestressed tension 
reinforcement. 

— A s / (l w &) 

= ratio of A s to bd 

= ratio of compression reinforcement, 

A r s to bd. 

= reinforcement ratio producing 
balanced strain conditions. 

- ratio of area of distributed 
longitudinal reinforcement to gross 
concrete area perpendicular to that 
reinforcement. 

= ratio of prestressed reinforcement, 
Ap S t o bd p . 

= ratio of volume of spiral 
reinforcement to total volume of core 
confined by the spiral, measured out- 
to-out of spirals. 

= ratio of area of distributed transverse 
reinforcement to gross concrete area 
perpendicular to that reinforcement. 

= ratio of tie reinforcement area to area 
of contact surface. 

= in 

b v s 

= ratio of tension reinforcement, A s to 

b w d. 

= strength-reduction factor. 


National, Structural Code of the Philippines Volume E ditto r 


4-20 CHAPTER 4 - Structural Concrete 


/ T cr 
T uncr 

*l>cp,N 

$cp,Na 

tyc.P 
*1* c.V 

*l>e 
\ Pec,N 
^ Pec,Na 

tyecy 

V'ed.JV 

*Ped,Na 

M*edy 

tyhy 


= stiffness reduction factor. 

= characteristic bond stress of adhesive 
anchor in cracked concrete, MPa. 

= characteristic bond stress of adhesive 
anchor in uncracked concrete, MPa. 

= factor used to modify development 
length based on cover. 

= factor used to modify tensile strength 
of anchors based on presence or 
absence of cracks in concrete. 

= factor used to modify tensile strength 
of post-installed anchors intended for 
use in uncracked concrete without 
supplementary reinforcement to 
account for the splitting tensile 
stresses due to installation. 

= factor used to modify tensile strength 
of adhesive anchors intended for use 
in uncracked concrete without 
supplementary reinforcement to 
account for the splitting tensile 
stresses due to installation. 

= factor used to modify pullout strength 
of anchors based on presence or 
absence of cracks in concrete. 

= factor used to modify shear strength 
of anchors based on presence or 
absence of cracks in concrete and 
presence or absence of 
supplementary reinforcement. 

= factor used to modify development 
length based on reinforcement 
coating. 

= factor used to modify tensile strength 
of anchors based on eccentricity of 
applied loads. 

= factor used to modify tensile strength 
of adhesive anchors based on 
eccentricity of applied loads. 

= factor used to modify shear strength 
of anchors based on eccentricity of 
applied loads. 

= factor used to modify tensile strength 
of anchors based on proximity to 
edges of concrete member. 

= factor used to modify tensile strength 
of adhesive anchors based on 
proximity to edges of concrete 
member. 

= factor used to modify shear strength 
of anchors based on proximity to 
edges of concrete member. 

= factor used to modify shear strength 
of anchors located in concrete 
members with h a < 1.5c al . 

= factor used to modify development 


length based on confining 
reinforcement. 

= factor used to modify development 
length based on reinforcement size. 
xf) t = factor used to modify development 

length for casting location intension. 
if> w = factor used to modify development 

length for welded deformed wire 
reinforcement in tension. 

Q o = amplification factor to account for 

overstrength of the seismic-force- 
resisting system determined in 
accordance with the general building 
code. 

a) w , a) pw , o)' w = reinforcement indices for flanged 
sections computed as for g>, 0) p and 
o) f except that b shall be the web 
width, and reinforcement area shall 
be that required to develop 
compressive strength of web only. 

402.3 Terminology 

ADHESIVE are chemical components formulated from 
organic polymers, or a combination of organic polymers 
and inorganic materials that cure if blended together. 

ADMIXTURE is a material other than water, aggregate, 
or hydraulic cement used as an ingredient of concrete and 
added to concrete before or during its mixing to modify 
its properties. 

AGGREGATE is a granular material, such as sand, 
gravel, crushed stone and iron blast-furnace slag, and 
when used with a cementing medium forms a hydraulic 
cement concrete or mortar. 

AGGREGATE, LIGHTWEIGHT is an aggregate 
meeting the requirements of ASTM C330 and having a 
bulk density with a dry, lose weight of 1 120 kg/m 3 or 
less, determined in accordance with ASTM C29. In some 
standards, the term lightweight aggregate is being 
replaced by the term low-density aggregate. 

ANCHOR is a steel element either cast into concrete or 
post-installed into a hardened concrete member and used 
to transmit applied loads to the concrete. 

ANCHOR, CAST-IN is a headed bolt, headed stud, or 
hooked bolt (J- or L-bolt) installed before placing 
concrete. 

ANCHOR, HEADED BOLT is a cast-in steel anchor 
that develops its tensile strength from the mechanical 
interlock provided by either a head or nut at the embedded 
end of the anchor. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 4 - Structural Concrete 


4 21 


ANCHOR, HOOKED BOLT is a cast-in anchor 
anchored mainly by bearing of the 90-degree bend (L- 
bolt) or 180-degree bend (J-bolt) against the concrete, at 
its embedded end, and having a minimum e ^ equal to 

3 d a . 

ANCHOR, HEADED STUD is a steel anchor 
conforming to the requirements of AWSD1.1M and 
affixed to a plate or similar steel attachment by the stud 
arc welding process before casting. 

ANCHOR, HORIZONTAL OR UPWARDLY 
INCLINED is an anchor installed in a hole drilled 
horizontally or in a hole drilled at any orientation above 
horizontal. 

ANCHOR, POST-INSTALLED, is an anchor installed 
in hardened concrete; adhesive, expansion, and undercut, 
anchors are examples of post-installed anchors. 

ANCHOR, ADHESIVE is a post-installed anchor, 
inserted into hardened concrete with an anchor hole 
diameter not greater than l.Stimes the anchor diameter, 
that transfers loads to the concrete by bond between the 
anchor and the adhesive, and bond between the adhesive 
and the concrete. 

ANCHOR, ADHESIVE-STEEL ELEMENTS are steel 
elements for adhesive anchors include threaded rods, 
deformed reinforcing bars, or internally threaded steel 
sleeves with external deformations. 

ANCHOR, EXPANSION is a post-installed anchor, 
inserted into hardened concrete that transfers loads to or 
from the concrete by direct bearing or friction or both. 

ANCHOR, UNDERCUT is a post-installed anchor that 
develops its tensile strength from the mechanical interlock 
provided by undercutting of the concrete at the embedded 
end of the anchor. Undercutting is achieved with a special 
drill before installing the anchor or alternatively by the 
anchor itself during its installation. 

ANCHOR GROUP is a number of similar anchors 
having approximately equal effective embedment depths 
with spacing s between adjacent anchors such that the 
protected areas overlap. 

ANCHOR PULLOUT STRENGTH is the strength 
corresponding to the anchoring device or a major 
component of the device sliding out from the concrete 
without breaking out a substantial portion of the 
surrounding concrete. 


ANCHORAGE DEVICE in post-tensioned members, the 
hardware used to transfer force from prestressed 
reinforcement to the concrete. 

ANCHORAGE DEVICE, BASIC MONOSTRAND is 

an anchorage device used with any single strand or a 
single 16mm. or smaller diameter bar that is in accordance 
with Sections 425.8.1,425.8.2 and 425,9.3.1a. 

ANCHORAGE DEVICE, BASIC MULTISTRAND is 

an anchorage device used with multiple strands, bars, or 
wires, or with single bars larger than 16 mm diameters 
that satisfies Sections 425.8.1, 425.8.2 and 425.9.3.1b. 

ANCHORAGE DEVICE, SPECIAL is an anchorage 
device that satisfies tests required in Section 425.9.3.1c. 

ANCHORAGE ZONE in post-tensioned members, 
portion of the member through which the concentrated 
prestressing force is transferred to the concrete and 
distributed more uniformly across the section; its extent is 
equal to the largest dimension of the cross section; for 
anchorage devices located away from the end of a 
member, the anchorage zone includes the disturbed 
regions ahead of and behind the anchorage device. 

ATTACHMENT is a structural assembly, external to the 
surface of the concrete that transmits loads to or receives 
loads from the anchor. 

B-REGION is a portion of a member in which it is 
reasonable to assume that strains due to flexure vary 
linearly through section. 

BASE OF STRUCTURE is a level at which the 
horizontal earthquake ground motions are assumed to be 
imparted to a building. This level does not necessarily 
coincide with the ground level. 

BEAM is a member subjected primarily to flexure and 
shear, with or without axial force or torsion; beams in a 
moment frame that forms part of the lateral-force-resisting 
system are predominantly horizontal members; a girder is 
a beam. 

BOUNDARY ELEMENT is a portion along wall and 
diaphragm edge, including edges of openings, 
strengthened by longitudinal and transverse 
reinforcement. 

BUILDING OFFICIAL is a term used in a general 
building code to identify the person charged with 
administration and enforcement of provisions of the 
building code. Such term as building inspector is a 
variation of the title, and the term “building official” as 


ISpoinea Volume } V 7 U ‘ Edition, 2015 


4-22 CHAPTER 4 - Structural Concrete 


used in this Code, is intended to include those variations, 
as^ell as others that are used in the same sense. 

CEMENTITIOUS MATERIALS are materials that 
have cementing value if used in concrete either by 
themselves, such as portland cement, blended hydraulic 
cements, and expansive cement, or such materials in 
combination with fly ash, raw or other calcined natural 
pozzolans, silica fume, and slag cement. 

COLLECTOR is an element that acts in axial tension or 
compression to transmit forces between a structural 
diaphragm and a vertical element of the seismic-force- 
resisting system. 

COLUMN is a member, usually vertical or predominantly 
vertical, used primarily to support axial compressive load, 
but that can also resist moment, shear, or torsion. Columns 
used as part of a lateral-force-resisting system resist 
combined axial load, moment, and shear. Refer to moment 
frame. 

COLUMN CAPITAL is an enlargement of the top of a 
concrete column located directly below the slab or drop 
panel that is cast monolithically with the column. 

COMPLIANCE REQUIREMENTS is a construction- 
related Code requirements directed to the contractor to be 
incorporated into construction documents by the licensed 
design professional, as applicable. 

COMPOSITE CONCRETE FLEXURAL MEMBERS 

are concrete flexural members of precast or cast-in-place 
concrete elements, constructed in separate placements but 
connected so that all elements respond to loads as a unit. 

COMPRESSION-CONTROLLED SECTION is a 

cross section in which the net tensile strain in the extreme 
tension reinforcement at nominal strength is less than or 
equal to the compression-controlled strain limit. 

COMPRESSION-CONTROLLED STRAIN LIMIT is 

a net tensile strain at balanced strain conditions. 

CONCRETE are mixture of portland cement or any other 
hydraulic cement, fine aggregate, coarse aggregate and 
water, with or without admixtures. 

CONCRETE, ALL-LIGHTWEIGHT is a lightweight 
concrete containing only lightweight coarse and fine 
aggregates that conform to ASTM C330. 

CONCRETE, LIGHTWEIGHT is a concrete 
containing lightweight aggregate and an equivalent 
density, as determined by ASTM C567, between 1440 
and 1840 kg/m 3 . 


CONCRETE, NON-PRESTRESSED is a reinforced 
concrete with at least the minimum amount of non- 
prestressed reinforcement and no prestressed 
reinforcement; or for two-way slabs, with less than the 
minimum amount of prestressed reinforcement. 

CONCRETE, N ORM ALWEIGHT is a concrete 
containing only aggregate that conforms to ASTM C33. 

CONCRETE, PLAIN is a concrete with no 
reinforcement or with less reinforcement than the 
minimum amount specified for reinforced concrete. 

CONCRETE, PRECAST is a concrete element cast 
elsewhere than its final position in the structure. 

CONCRETE, PRESTRESSED is a concrete in which 
internal stresses have been introduced to reduce potential 
tensile stresses in concrete resulting from service loads. 

CONCRETE, REINFORCED is a concrete reinforced 
with at least the minimum amounts of non-prestressed or 
prestressed reinforcement required by this Code. 

CONCRETE, SAND-LIGHTWEIGHT is a concrete 
containing only normal weight fine aggregate that 
conforms to ASTM C33M and lightweight coarse 
aggregate that conforms to ASTM C330M. 

CONCRETE, STEEL FIBER-REINFORCED is a 

concrete containing a prescribed amount of dispersed, 
randomly oriented, discontinuous deformed steel fibers. 

concrete Strength, specified 

COMPRESSIVE is a compressive strength of concrete 
used in design and evaluated in accordance with 
provisions of this Code, MPa. Whenever the quantity f c 
is under a radical sign, square root of numerical value 
only is intended, and result has units of MPa. 

CONCRETE BREAKOUT STRENGTH is a strength 
corresponding to a volume of concrete surrounding the 
anchor or group of anchors separating from the member. 

CONCRETE PRYOUT STRENGTH is a strength 
corresponding to formation of a concrete spall behind 
short, stiff anchors displaced in the direction opposite to 
the applied shear force. 

CONNECTION is a region of a structure that joins two 
or more members; a connection also refers to a region that 
joins members of which one or more is precast. 

CONNECTION, DUCTILE is a connection that 
experiences yielding as a result of the earthquake design 
displacements. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHART ER 4 - Structural Concrete 


T 23 


CONNECTION, STRONG is a connection between 
one or more precast elements that remains elastic while 
adjoining members experience yielding as a result of the 
earthquake design displacements. 

CONTRACT DOCUMENTS is a written and graphic 
documents and specifications prepared or assembled for 
describing the location, design, materials, and physical 
characteristics of the elements of a project necessary for 
obtaining a building permit and construction of the 
project. 

CONTRACTION JOINT is a formed, sawed, or tooled 
groove in a concrete structure to create a weakened plane 
and regulate the location of cracking resulting from the 
dimensional change of different parts of the structure. 

COVER, SPECIFIED CONCRETE is a distance 
between the outermost surface of embedded 
reinforcement and the closest outer surface of the 
concrete. 

CROSSTIE is a continuous reinforcing bar having a 
seismic hook at one end and a hook not less than 90- 
degree hooks with at least six-diameter extension at the 
other end. The hooks shall engage peripheral longitudinal 
bars. The 90-degree hooks of two successive crossties 
engaging the same longitudinal bars shall be alternated 
end for end, 

D-REGION is a portion of a member within a distance, 
h , from a force discontinuity or a geometric discontinuity 

DESIGN DISPLACEMENT is a total calculated lateral 
displacement expected for the design-basis earthquake. 

DESIGN INFORMATION is project-specific 
information to be incorporated into construction 
documents by the licensed design professional, as 
applicable. 

DESIGN LOAD COMBINATION is a combination of 
factored loads and forces. 

DESIGN STOREY DRIFT RATIO is a relative 
difference of design displacement in between the top and 
bottom of a storey, divided by the story height. 

DEVELOPMENT LENGTH is a length of embedded 
reinforcement, including prestressing strand, required to 
develop the design strength of reinforcement at a critical 
section. 

DISCONTINUITY is an abrupt change in geometry or 
loading. 


DISTANCE SLEEVE is a sleeve that encases the center 
part of an undercut anchor, a torque-controlled expansion 
anchor, or a displacement-controlled expansion anchor, 
but does not expand. 

DROP PANEL is a projection below the slab used to 
reduce the amount of negative reinforcement over a 
column or the minimum required slab thickness, and to 
increase the slab shear strength. 

DUCT is a conduit, plain or corrugated, to accommodate 
prestressing reinforcement for post-tensioning 
applications. 

DURABILITY is an ability of a structure or member to 
resist deterioration that impairs performance or limits 
service life of the structure in the relevant environment 
considered in design. 

EDGE DISTANCE is a distance from the edge of the 
concrete surface to the center of the nearest anchor. 

EFFECTIVE DEPTH OF SECTION is a distance 
measured from extreme compression fiber to centroid of 
tension reinforcement. 

EFFECTIVE EMBEDMENT DEPTH is an overall 
depth through which the anchor transfers force to or from 
the surrounding concrete; effective embedment depth will 
normally be the depth of the concrete failure surface in 
tension applications; for cast-in headed anchor bolts and 
headed studs, the effective embedment depth is measured 
from the bearing contact surface of the head. 

EFFECTIVE PRESTRESS is a stress remaining in 
prestressing reinforcement after all losses in Section 
420.3.2.6 have occurred. 

EMBEDMENTS is an items embedded in concrete, 
excluding reinforcement as defined in Section 420 and 
anchors as defined in Section 417. Reinforcement or 
anchors welded, bolted or otherwise connected to the 
embedded item to develop the strength of the assembly are 
considered to be part of the embedment. 

EMBEDMENTS, PIPE is an embedded pipes, conduits, 
and sleeves. 

EMBEDMENT LENGTH is a length of embedded 
reinforcement provided beyond a critical section. 

EQUILIBRIUM DENSITY is a density of lightweight 
concrete determined in accordance with ASTMC 567 
after exposure to a relative humidity of 50 ± 5 percent and 
a temperature of 23 ± 2.00 °C for a period of time 
sufficient to reach constant density. 


National Structural Code of the Philippines Volume 1 


4-24 CHAPTER 4 - Structural Concrete 


EXPANSION SLEEVE is an outer part of an expansion 
anchor that is forced outward by the center part, either by 
applied torque or impact, to bear against the sides of the 
predrilled hole. Refer to anchor, expansion. 

EXTREME TENSION REINFORCEMENT is a layer 
of prestressed or non-prestressed reinforcement that is the 
farthest from the extreme compression fiber. 

FINITE ELEMENT ANALYSIS is a numerical 
modeling technique in which a structure is divided into a 
number of discrete elements for analysis. 

FIVE PERCENT FRACTILE is a statistical term 
meaning 90 percent confidence that there is 95 percent 
probability of the actual strength exceeding the nominal 
strength. 

HEADED DEFORMED BARS is a deformed 
reinforcing bars with heads attached at one or both ends. 

HEADED SHEAR STUD REINFORCEMENT is a 

reinforcement consisting of individual headed studs or 
groups of studs, with anchorage provided by a head at 
each end, or by a head at one end and a common base rail 
consisting of a steel plate or shape at the other end. 

HOOP is a closed tie or continuously wound tie. A closed 
tie, made up of one or several reinforcement elements, 
each having seismic hooks at both ends. A closed tie shall 
not be made up of interlocking headed deformed bars. 
Section 425.7.4. 

INSPECTION is an observation, verification, and 
required documentation of the materials, installation, 
fabrication, erection or placement of components and 
connections to determine compliance with construction 
documents and referenced standards. 

INSPECTION, CONTINUOUS is the full time 
observation, verification, and required documentation of 
work in the area where the work is being performed. 

INSPECTION, PERIODIC is the part-time or 
intermittent observation, verification, and required 
documentation of work in the area where the work is 
being performed. 

ISOLATION JOINT is a separation between adjoining 
parts of a concrete structure, usually a vertical plane, at a 
designed location such as to interfere least with 
performance of the structure* yet such as to allow relative 
movement in three directions and avoid formation of 
cracks elsewhere in the concrete and through which all or 
part of the bonded reinforcement is interrupted. 


JACKING FORCE In prestressed concrete, temporary 
force exerted by device that introduces tension into 
prestressing reinforcement. 

JOINT is a portion of structure common to intersecting 
members. 

LICENSED DESIGN PROFESSIONAL is an 
individual who is licensed to practice structural design as 
defined by the statutory requirements of the Professional 
Regulation Commission (PRC) or jurisdiction in which 
the project is to be constructed and who is in responsible 
charge of the structural design. 

LOAD are forces or other actions that result from the 
weight of all building materials, occupants, and their 
possessions, environmental effects, differential movement, 
and restrained dimensional changes; permanent loads are 
those loads in which variations over time are rare or of 
small magnitude; all other loads are variable loads. 

LOAD, DEAD is the weight of the members, supported 
structure, and permanent attachments or accessories that 
are likely to be present on a structure in service; or loads 
meeting specific criteria found in the general building 
code; without load factors. 

LOAD, FACTORED is a load, multiplied by appropriate 
load factors. 

LOAD, LIVE is a load that is not permanently applied to 
a structure, but is likely to occur during the service life of 
the structure (excluding environmental loads); or loads 
meeting specific criteria found in the general building 
code; without load factors. 

LOAD, ROOF LIVE is a load on a roof produced during 
maintenance by workers, equipment, and materials, and 
during the life of the structure by movable objects, such as 
planters or other similar small decorative appurtenances 
that are not occupancy related; or loads meeting specific 
criteria found in the general building code; without load 
factors. 

LOAD, SERVICE are all loads, static or transitory, 
imposed on a structure or element thereof, during the 
operation of a facility, without load factors. 

LOAD PATH are sequence of members and connections 
designed to transfer the factored loads and forces in such 
combinations as are stipulated in this Code, from the point 
of application or origination through the structure to the 
final support location or the foundation. 

MANUFACTURER’S PRINTED INSTALLATION 
INSTRUCTIONS (MPII) published instructions for the 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER a - Structural Concrete 




correct installation of the anchor under all covered 
installation conditions as supplied in the product 
packaging. 

MODULUS OF ELASTICITY is a ratio of normal 
stress to corresponding strain for tensile or compressive 
stresses below proportional limit of material. 

MOMENT FRAME is a frame in which beams, slabs, 
columns, and joints resist forces predominantly shear, and 
axial force; Beams or slabs are predominantly horizontal 
or nearly horizontal; Columns are predominantly vertical 
or nearly vertical. 

MOMENT FRAME, ORDINARY is a cast-in-place or 
precast concrete beam-column or slab-column frame 
complying with Section 418.3. 

MOMENT FRAME, INTERMEDIATE is a cast-in- 
place frame or two-way slab-column frame beams 
complying with Section 418.4. 

MOMENT FRAME, SPECIAL is a cast-in-place 
beam-column frame complying with Sections 418.2.3 
through 418.2.8; and, Sections 418,6 through 418.8. A 
precast beam-column frame complying with Sections 
418.2.3 through 418.2.8 and 418.9. 

NET TENSILE STRAIN is a tensile strain at nominal 
strength exclusive of strains due to effective prestress, 
creep, shrinkage and temperature. 

NODAL ZONE is a volume of concrete around a node 
that is assumed to transfer strut-and-tie forces through the 
node. 

NODE is a point in a strut-and-tie model where the axes 
of the struts, ties, and concentrated forces acting on the 
joint intersect. 

ONE-WAY CONSTRUCTION is members designed to 
be capable of supporting all loads through bending in a 
single direction; refer to two-way construction. 

PEDESTAL is a member with a ratio of height-to-least 
lateral dimension less than or equal to three used 
primarily to support axial compressive load; for a tapered 
member, the least lateral dimension is the average of the 
top and bottom dimensions of the smaller side. 

PLASTIC HINGE REGION is a length of frame 
element over which flexural yielding is intended to occur 
due to earthquake design displacements, extending not 
less than a distance h from the critical section where 
flexural yielding initiates. 


POST-TENSIONING is a method of prestressing in 
which prestressing reinforcement is tensioned after 
concrete has hardened. 

PRECOMPRESSED TENSILE ZONE is a portion of a 
prestressed member where flexural tension, calculated 
using gross section properties, would occur under service 
loads if the prestress force was not present. 

PRETENSIONING is a method of prestressing in which 
prestressing reinforcement is tensioned before concrete is 
cast. 

PROJECTED AREA is an area on the free surface of the 
concrete member that is used to represent the larger base 
of the assumed rectilinear failure surface. 

PROJECTED INFLUENCE AREA is a rectilinear area 
on the free surface of the concrete member that is used to 
calculate the bond strength of adhesive anchors. 

REINFORCEMENT is a steel element or elements 
embedded in concrete and conforming to Sections 420.2 
through 420.5. Prestressed reinforcement in external 
tendons is also considered reinforcement. 

REINFORCEMENT, DEFORMED is a deformed bars, 
welded bar mats, deformed wire, and welded wire 
reinforcement conforming to Sections 420.2, 1 .3, 
420.2. 1 ,5, or 420.2. 1 .7, excluding plain wire. 

REINFORCEMENT, PLAIN are bars or wires 
conforming to Section 420.2.1.4 or 420.2.1.7 that do 
not conform to definition of deformed reinforcement. 

REINFORCEMENT, PRESTRESSED is a prestressing 
reinforcement that has been tensioned to impart forces to 
concrete. 

REINFORCEMENT, BONDED PRESTRESSED is a 

pretensioned reinforcement or prestressed reinforcement 
in a bonded tendon. 

REINFORCEMENT, PRESTRESSING is a high- 
strength reinforcement such as strand, wire, or bar 
conforming to Section 420.3.1. 

REINFORCEMENT, WELDED WIRE is a plain or 
deformed wire fabricated into sheets or rolls conforming 
to Section 420.2.1.7, 

REINFORCEMENT, WELDED DEFORMED 
STEEL BAR MAT is a mat conforming to Section 
420,2.1.5 consisting of two layers of deformed bars at 
right angles to each other welded at the intersections. 










4-26 CHAPTER 4 - Structural Concrete 


REINFORCEMENT, ANCHOR is an reinforcement 
used t* transfer the full design load from the anchors into 
the structural member. 

REINFORCEMENT, SUPPLEMENTARY is a 

reinforcement that acts to restrain the potential concrete 
breakout but is not designed to transfer the full design 
load from the anchors into the structural member. 

SEISMIC DESIGN CATEGORY is a classification 
assigned to a structure based on its occupancy category 
and the severity of the design earthquake ground motion 
at the site, as defined in Section 402 of this Code. 

SEISMIC-FORCE-RESISTING SYSTEM is a portion 
of the structure designed to resist earthquake effects 
required by the legally adopted general building code 
using the applicable provisions and load combinations. 

SEISMIC HOOK is a hook on a stirrup, or crosstie 
having a bend not less than 135 degrees, except that 
circular hoops shall have a bend not less than 90 degrees, 
hooks shall have a 6 d b , but not less than 75 mm. The 
hooks shall engage the longitudinal reinforcement and the 
extension shall project into the interior of the stirrup or 
hoop. 

SHEAR CAP is a projection below the slab used to 
increase the slab shear strength. 

SHEATHING is a material encasing prestressing 
reinforcement to prevent bonding of the prestressing 
reinforcement with the surrounding concrete, to provide 
corrosion protection, and to contain the corrosion 
inhibiting coating. 

SPACING is a center-to-center distance between adjacent 
items, such as longitudinal reinforcement, transverse 
reinforcement, prestressing reinforcement, or anchors. 

SPACING, CLEAR is a least dimension between the 
outermost surfaces of adjacent items. 

SPAN LENGTH is a distance between supports. 

SPECIAL SEISMIC SYSTEMS is a structural systems 
that use special moment frames, special structural walls, 
or both. 

SPECIALTY INSERT is a predesigned and 
prefabricated cast-in anchors specifically designed for 
attachment of bolted or slotted connections. 

SPIRAL REINFORCEMENT is a continuously wound 
reinforcement in the form of a cylindrical helix. 


SPLITTING TENSILE STRENGTH is a tensile 
strength of concrete determined in accordance with 
ASTM C496M as described in "Specifications for 
Lightweight Aggregate for Structural Concrete ” ("ASTM 
C330). 

STEEL ELEMENT, BRITTLE is an element with a 
tensile test elongation of less than 14 percent, or reduction 
in area of less than 30 percent at failure. 

STEEL ELEMENT, DUCTILE is an element with a 
tensile test elongation of at least 14 percent and reduction 
in area of at least 30 percent; Steel element meeting the 
requirements ol ASTM A307 shall be considcied ductile, 
except as modified by for earthquake effects, deformed 
reinforcing bars meeting the requirements of ASTM 
A615M, A706M, or A955M shall be considered as ductile 
steel elements. 

STIRRUP is an reinforcement used to resist shear and 
torsion stresses in a structural member; typically 
deformed bars, deformed wires, or welded wire 
reinforcement either single leg or bent into L, U or 
rectangular shapes and located perpendicular to or at an 
angle to longitudinal reinforcement. Refer to "tie." 

STRENGTH, DESIGN is a nominal strength multiplied 
by a strength reduction factor, (f). 

STRENGTH, NOMINAL is strength of a member or 
cross section calculated in accordance with provisions and 
assumptions of the strength design method of this chapter 
before application of any strength reduction factors. 

STRENGTH, REQUIRED is strength of a member or 
cross section required to resist factored loads or related 
internal moments and forces in such combinations as are 
stipulated in this chapter. 

STRESS is the intensity of force per unit area. 

STRESS LENGTH is a length of anchor, extending 
beyond concrete in which it is anchored, subject to full 
tensile load applied to anchor, and for which cross- 
sectional area is minimum and constant. 

STRUCTURAL CONCRETE is a concrete used for 
structural purposes, including plain and reinforced 
concrete. 

STRUCTURAL DIAPHRAGM is a member, such as a 
floor or roof slab, that transmits forces acting in the plane 
of the member to the vertical elements of the seismic- 
force-resisting system. A structural diaphragm may 
include chords and collectors as part of the diaphragm. 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




STRUCTURAL INTEGRITY is an ability of a structure 
through strength, redundancy, ductility, and detailing of 
reinforcement to redistribute stresses and maintain overall 
stability if localized damage or significant overstress 
occurs. 

STRUCTURAL SYSTEM interconnected members 
designed to meet performance requirements. 

STRUCTURAL TRUSS is an assemblage of reinforced 
concrete members subjected primarily to axial forces. 

STRUCTURAL WALL is a wall proportioned to resist 
combinations of shears, moments, and axial forces in the 
plane of the wall; a shear wall is a structural wall. 

STRUCTURAL WALL, ORDINARY REINFORCED 
CONCRETE is a wall complying with the requirements 
of Sections 411. 

STRUCTURAL WALL, ORDINARY PLAIN 
CONCRETE is a wall complying with the 

requirements of Section 414. 

STRUCTURAL WALL, INTERMEDIATE 
PRECAST is a wall complying with Section 418.5. 

STRUCTURAL WALL, SPECIAL is a cast-in-place 
structural wall in accordance with Sections 418.2,3 
through 418.2.8 and 418.10; or precast structural wall 
accordance with Sections 418.2.3 through 418.2.8 and 
418.11. 

STRUT is a compression member in a strut-and-tie model 
representing the resultant of a parallel or a fan-shaped 
compression field. 

STRUT, BOTTLE-SHAPED is a strut that is wider at 
mid-length than at its ends. 

STRUT-AND-TIE MODEL is a truss model of a 
structural member or of a D-region in such a member, 
made up of struts and ties connected at nodes, capable of 
transferring the factored loads to the supports or to 
adjacent B-regions. 

TENDON In post-tensioned members, a tendon is a 
complete assembly consisting of anchorages, prestressing 
reinforcement, and sheathing with coating for unbounded 
applications or ducts filled with grout for bonded 
applications. 

TENDON, BONDED is a tendon in which prestressed 
reinforcement is continuously bonded to the concrete 
through grouting of ducts embedded within the concrete 
cross section. 


TENDON, EXTERNAL is a tendon external to the 
member concrete cross section in post-tensioned 
applications. 

TENDON, UNBONDED is a tendon in which prestressed 
reinforcement is prevented from bonding to the concrete. 
The prestressing force is permanently transferred to the 
concrete at the tendon ends by the anchorages only. 

TENSION-CONTROLLED SECTION is a cross 
section in which the net tensile strain in the extreme 
tension steel at nominal strength is greater than or equal to 

0 . 005 , 

TIE is a loop of reinforcing bar or wire enclosing 
longitudinal reinforcement; a continuously wound bar or 
wire in the form of a circle, rectangle, or other polygon 
shape without re-entrant comers is acceptable; refer to 
stirrup or hoop; or a tension member in a strut-and-tie 
model. 

TRANSFER is an act of transferring stress in 
prestressing reinforcement from jacks or pretensioning 
bed to concrete member. 

TRANSFER LENGTH is a length of embedded 
pretensioned reinforcement required to transfer the 
effective prestress to the concrete. 

TWO-WAY CONSTRUCTION are members designed 
to be capable of supporting loads through bending in two 
directions; Some slabs and foundations are considered 
two-way construction. Refer to one-way construction. 

WALL is a vertical element designed to resist axial load, 
lateral load, or both, with a horizontal length-to-thickness 
ratio greater than three, used to enclose or separate spaces. 

WALL SEGMENT is a portion of wall bounded by 
vertical or horizontal openings or edges. 

WALL SEGMENT, HORIZONTAL is a segment of 
a structural wall, bounded vertically by two openings or 
by an opening and an edge. 

WALL SEGMENT, VERTICAL is a segment of a 
structural wall, bounded horizontally by two openings or 
by an opening and an edge; Wall piers are vertical wall 
segments. 

WALL PIER is a vertical wall segments with dimensions 
and reinforcement intended to result in shear demand 
being limited by flexural yielding of the vertical 
reinforcement in the pier. 


4-28 CHAPTER 4 - Structural Concrete 


WATER-CEMENTITIOUS MATERIALS RATIO is a 
ratio of mass of water, excluding tiial absorbed by the 
aggregate, to the mass of cementitious materials in a 
mixture, stated as a decimal. 

WORK is the entire construction or separately 
identifiable parts thereof that are required to be furnished 
under the construction documents. 

YIELD STRENGTH is a specified minimum yield 
strength or yield point of reinforcement; yield strength or 
yield point shall be determined in tension according to 
applicable A STM standards as modified by this section. 


SECTION 403 

REFERENCED STANDARDS 


403.1 Standards, or specific sections thereof, cited in 
this Code, including Annex, Appendices, or Supplements 
where prescribed, are referenced without exception in this 
Code, unless specifically noted. Cited standards are listed 
in the following with their serial designations, including 
year of adoption or revision. 

403.2 Referenced Standards 

403.2.1 American Association of State Highway and 
Transportation Officials (AASHTO) 


Artic le Dc s i “i nitio n 
Article 5.10.9.6 
Article 5.10.9.7.2 
Article 5.10.9.7.3 

Article 10.3.2.3 


Title _ 

AASHTO LRFD Bridge 
Design Specifications, 

6th Edition, 2012 
AASHTO LRFD Bridge 
Construction Specifications, 
3rd Edit ion, 2010 


403.2.2 American Concrete Institute (ACI) 


Standard/ Section 
Designation 

Section 4.2.3 of 
ACI 301-10 

ACI 318.2-14 
ACI 332-14 


ACI 355.2-07 


ACI 355.4-11 


ACI374.1-05 


ACI 423.7-07 


ACI ITG-5. 1-07 


Specifications for Structural Concrete 

Building Code Requirements for 

' Concrete Thin Shells 

Residential Code Requirements for 
Struct ural Concrete and Commentary 
~ Qualification of Post-Installed 
Mechanical Anchors in Concrete and 

Commentary 

Qualification of Post- 
Installed Adhesive Anchors in 

Concrete 

Acceptance Criteria for Moment 
Frames Based on Structural Testing 
Specification for Unbonded Single- 

Strand Tendon Materials 

Acceptance Criteria for Special 
Unbonded Post-Tensioned Precast 
Structural Walls Based on Validation 
Testing 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 




CHAPTER 4 - Structural Concrete 


4-29 


403.2.3 American Society of Civil Engineers 
(ASCE)/Structural Engineering Institute (SEI) 


Section 

Designation 

Title 

Section 2.3.3. 

Load Combinations 
including Flood Loads 

ASCE/SEI 7-10 Minimum 
Design Loads for Buildings 
and Other Structures 

Section 2.3.4, 

Load Combinations 
excluding Atmospheric 

Ice Loads 


403.2.4 ASTM International 


Standard 

Designation 

Title 

A36/A36M-12 

Standard Specification for 
Carbon Structural Steel 

A53/A53M-12 

Standard Specification for Pipe, 
Steel, Black and Hot-Dipped, 
Zinc-Coated, Welded and 
Seamless 

A184/A184M-06 

(2011) 

Standard Specification for 
Welded Deformed Steel Bar 
Mats for Concrete 
Reinforcement 

A242/A242M-04 

(2009) 

Standard Specification for High- 
Strength Low-Alloy Structural 
Steel 

A307-12 

Standard Specification for 
Carbon Steel Bolts, Studs, and 
Threaded Rod, 420 MPa Tensile 
Strength 

A416/A416M-12a 

Standard Specification for 

Steel Strand, Uncoated Seven- 
Wire for Prestressed Concrete 

A421/A421M-10 

Standard Specification for 
Uncoated Stress-Relieved Steel 
Wire for Prestressed Concrete 
including Supplementary 
Requirement I, 

Low- Relaxation Wire 

A5 00/A5 00M- 1 0a 

Standard Specification for 

Cold- Formed Welded and 
Seamless Carbon Steel 
Structural Tubing in Rounds 
and Shapes 

A501-07 

Standard Specification for Hot- 
Formed Welded and Seamless 
Carbon Steel Structural Tubing 

A572/A572M-12a 

Standard Specification for 

High- Strength Low-Alloy 
Columbium- Vanadium 
Structural Steel 


Standard 

Designation 

Title 

A588/A588M-10 

Standard Specification for - 
High- Strength Low-Alloy 
Structural Steel, up to 345 MPa 
Minimum Yield Point, with 
Atmospheric Corrosion 
Resistance 

A615/A615M-12 

Standard Specification for 
Deformed and Plain Carbon- 
Steel Bars for Concrete 
Reinforcement 

A706/A706M-09b 

Steel Deformed and Plain 

Bars for Concrete 
Reinforcement 

A722/A722M-12 

Standard Specification for 
Uncoated High-Strength Steel 
Bars for Prestressing Concrete 

A767/A767M-09 

Standard Specification for Zinc- 
Coated (Galvanized) Steel Bars 
for Concrete Reinforcement 

A775/A775M-07b 

Standard Specification for 
Epoxy-Coated Steel 
Reinforcing Bars 

A820/A820M-1 1 

Standard Specification for Steel 
Fibers for Fiber-Reinforced 
Concrete 

A884/A884M-12 

Standard Specification for 
Epoxy- Coated Steel Wire and 
Welded Wire Reinforcement 

A934/A934M-07 

Standard Specification for 
Epoxy- Coated Prefabricated 
Steel Reinforcing Bars 

A955/A955M-12 cl 

Standard Specification for 
Deformed and Plain Stainless- 
Steel Bars for Concrete 
Reinforcement 

A970/A970M-12 

Standard Specification for 
Headed Steel Bars for 
Concrete Reinforcement 
including Annex A1 
Requirements or Class HA 
Headed Dimensions 

A992/A992M-1 1 

Standard Specification for 
Structural Steel Shapes 

A996/A996M-09b 

Standard Specification for Rail- 
Steel and Axle-Steel Deformed 

Bars for Concrete 
Reinforcement 

A 1 022/A 1 022M-07 

Standard Specification for 
Deformed and Plain Stainless 

Steel Wire and Welded Wire 
for Concrete Reinforcement 


National Structural Code of the Philippines Volume I, 7 th Edition, 2015 


4-30 CHAPTER 4 - Structural Concrete 


Standard 

Designation 

Title 

A1035/A1035M-1 1 

Standard Specification for 

Deformed and Plain, Low- 
Carbon, Chromium, Steel Bars 
for Concrete Reinforcement 

A 1 044/A 1 044M-05 
(2010) 

Standard Specification for Steel 

Stud Assemblies for Shear 
Reinforcement of Concrete 

A1055/A1055M-10 cl 

Standard Specification for Zinc 
and Epoxy Dual-Coated Steel 
Reinforcing Bars 

A 1 060/ A 1 060M- 1 1 cl 

Standard Specification for Zinc- 
Coated (Galvanized) Steel 
Welded Wire Reinforcement, 
Plain and Deformed, for 
Concrete 

A 1 064/A 1 064M- 1 2 

Standard Specification for 

Carbon- Steel Wire and Welded 
Wire Reinforcement, Plain and 
Deformed, for Concrete 

C29/C29M-09 

Standard Test Method for 

Bulk Density(“Unit Weight”) 
and Voids in Aggregate 

C31/C31M-12 

Standard Practice for 

Making and Curing Concrete 
Test Specimens in the Field 

C33/C33M-13 

Standard Specification for 
Concrete Aggregates 

C39/C39M-12a 

Standard Test Method for 
Compressive Strength of 
Cylindrical Concrete Specimens 

C42/C42M-13 

Standard Test Method for 

Obtaining and Testing Drilled 
Cores and Sawed Beams of 
Concrete 

C94/C94M-12a 

Standard Specification for 

Ready- Mixed Concrete 

C144-11 

Standard Specification for 
Aggregate for Masonry Mortar 

C150/C150M-12 

Standard Specification for 
Portland Cement 

C172/C172M-10 

Standard Practice for Sampling 
Freshly Mixed Concrete 

C173/173M-12 

Standard Test Method for Air 

Content of Freshly Mixed 
Concrete by the Volumetric 
Method 

C231/C231M-10 

Standard Test Method for Air 
Content of Freshly Mixed 
Concrete by the Pressure 
Method 

C260/C260M-10a 

Standard Specification for 
Air-Entraining Admixtures 

For Concrete 


Standard 

Designation 

Title 

C330/C330M-09 

Standard Specification for 

Lightweight Aggregates for 
Structural Concrete 

C496/C496M-1 1 

Standard Test Method for 

Splitting Tensile Strength of 
Cylindrical Concrete Specimens 

C567/C567M-1 1 

Standard Test Method or 
Determining Density of 
Structural Lightweight Concrete 

C595/C595M-12 cl 

Standard Specification for 

Blended Hydraulic Cements 

C618-12a 

Standard Specification for Coal 

Fly Ash and Raw or Calcined 
Natural Pozzolan for Use in 
Concrete 

C685/C685M-1 1 

Standard Specification for 

Concrete Made by Volumetric 
Batching and Continuous 
Mixing 

C845/C845M-12 

Standard Specification for 
Expansive Hydraulic Cement 

C989/C989M-12a 

Standard Specification for Slag 

Cement for Use in Concrete and 
Mortars 

C1012/C1012M-13 

Standard Test Method for 

Length Change of Hydraulic- 
Cement Mortars Exposed to a 
Sulfate Solution 

C1017/C1017M-07 

Standard Specification for 
Chemical Admixtures for Use in 
Producing Flowing Concrete 

C1077-13 

Standard Practice for 
Laboratories Testing Concrete 
and Concrete Aggregates for 
Use in Construction and 
Criteria for Laboratory 
Evaluation 

Cl 1 16/Cl 16M-10a 

Standard Specification for Fiber- 
Reinforced Concrete 

Cl 157/Cl 157M-11 

Standard Performance 
Specification for Hydraulic 
Cement 

C1218/1218M- 

99(2008) 

Standard Test Method for 
Water-Soluble Chloride in 
Mortar and Concrete 

C1240-12 

Standard Specification for Silica 

Fume Used in Cementitious 
Mixtures 

C1580-09 cl 

Standard Test for 
Water-Soluble Sulfate in Soil 

C1582/C1582M-1 1 

Standard Specification for 

Admixtures to Inhibit Chloride- 
Induced Corrosion of 
Reinforcing Steel in Concrete 


Association of Structural Engineers of the Philippines, Inc. (ASEP) 


CHAPTER 4 — Structural Concrete 


4-31 


Standard 

Designation 

Title 

C 1 602/C 1602M- 12 

Standard Specification for 
Mixing Water Used in the 
Production of Hydraulic Cement 
Concrete 

C 1 609/C 1609M- 12 

Standard Test Method for 
Flexural Performance of Fiber- 
Reinforced Concrete (Using 
Beam With Third- Point 
Loading) 

D516-11 

Standard Test Method for 
Sulfate Ion in Water 

D4 130-08 

Standard Test Method for 
Sulfate Ion in Brackish Water, 
Seawater, and Brines 


403.2.5 American Welding Society (AWS) 


Standard 

Designation 

Title 

A WS D1.4/D1.4M: 
2011 

Structural Welding Code 
Reinforcing Steel 

AWS D1.1/D1.1M: 

2010 

Structural Welding Code 

Steel 


403.2.6 Australian Standard (AS) and New Zealand 
Standard (NZS) 


Standard 

Designation 

Title 

AS/NZS 4671: 2001 

Steel Reinforcing 

Material 

NZS 3101: 2006 

Part 1& Part 2 

Concrete Structures Standard 
Design of Concrete Structures 

NZS 3109 
Amendment 2 

Welding of Reinforcing Steel 

AS/NZS 1554.3: 2008 
Part 3 

Structural Steel Welding- 
Welding of Reinforcing Steel 


SECTION 404 
STRUCTURAL SYSTEM 
REQUIREMENTS 

404.1 Scope 

404.1.1 This section shall apply to design of structural 
concrete in structures or portions of structures defined in 
Section 401. 

404.2 Materials 

404.2.1 Design properties of concrete shall be selected 
to be in accordance with Section 419. 

404.2.2 Design properties of reinforcement shall be 
selected to be in accordance with Section 420. 

404.3 Design Loads 

404.3.1 Loads and load combinations considered in 
design shall be in accordance with Section 405. 

404.4 Structural System and Load Paths 

404.4.1 The structural system shall include (a) through 
(g), as applicable: 

a. Floor construction and roof construction, including 
one-way and two-way slabs; 

b. Beams and joists; 

c. Column; 

d. Wall; 

e. Diaphragms; 

f. Foundations; 


g. Joints, connections, and anchors as required to 
transmit forces from one component to another. 

404.4.2 Design of structural members including joints 
and connections given in Section 404.4.1 shall be in 
accordance with Sections 407 through 418. 

404.4.3 It shall be permitted to design a structural 
system comprising structural members not in accordance 
with Sections 404.4.1 and 404.4.2, provided the structural 
system is approved in accordance with Section 401.10.1. 


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4-32 CHAPTER 4 - Structural Concrete 


404.4.4 The structural system shall be designed to resist 
the factored loads in load combinations given in Section 

404.3 without exceeding the appropriate member design 
strengths, considering one or more continuous load paths 
from the point of load application or origination to the 
final point of resistance. 

404.4.5 Structural systems shall be designed to 
accommodate anticipated volume change and differential 
settlement. 

404.4.6 Seismic-Force-Resisting System 

404.4.6.1 Every structure shall be assigned to a seismic 
zones 4, or 2, in accordance with the general building 
code or as determined by the authority having jurisdiction 
in areas without a legally adopted building code. 

404.4.6.2 Structural systems designated as part of the 
seismic-force-resisting system shall be restricted to those 
systems designated by the general building code or as 
determined by the authority having jurisdiction in areas 
without a legally adopted building code. 


404.4.7.4 Diaphragms shall be designed to resist 
applicable lateral loads from soil and hydrostatic pressure 
and other loads assigned to the diaphragm by structural 
analysis. 

404.4.7.5 Collectors shall be provided where required to 
transmit forces between diaphragms and vertical 
elements. 

404.4.7.6 Diaphragms that are part of the seismic-force- 
resisting system shall be designed for the applied forces. 
In structures assigned to seismic zone 4, the diaphragm 
design shall be in accordance with Section 418. 

404.5 Structural Analysis 

404.5.1 Analytical procedures shall satisfy 
compatibility of deformations and equilibrium of forces. 

404.5.2 The methods of analyses given in Section 406 
shall be permitted. 

404.6 Strength 


404.4.6.3 Structural systems assigned to seismic zone 2 
shall satisfy the applicable requirements of this Code. 
Structures assigned to seismic zone 2 are not required to 
be designed in accordance with Section 418. 

404.4.6.4 Structural systems assigned to seismic zone 4 
shall satisfy the requirements of Section 418 in addition to 
applicable requirements of other sections of this Code. 

404.4.6.5 In structures assigned to seismic zone 4, 
structural members assumed not to be part of the seismic- 
force-resisting system shall be permitted, provided their 
effect on the response of the system is considered and 
accommodated in the structural design. Consequences of 
damage to structural and nonstructural members that are 
not a part of the seismic-force-resisting system shall be 
considered. 

404.4.7 Diaphragms 

404.4.7.1 Diaphragms, such as floor or roof slabs, shall 
be designed to resist simultaneously both out-of-plane 
gravity loads and in-plane lateral forces in load 
combinations given in Section 404.3. 

404.4.7.2 Diaphragms and their connections to framing 
members shall be designed to transfer forces between the 
diaphragm and framing members. 

404.4.7.3 Diaphragms and their connections shall be 
designed to provide lateral support to vertical, horizontal, 
and inclined elements. 


404.6.1 Design strength of a member and its joints and 
connections, in terms of moment, axial force, shear, 
torsion, and bearing, shall be taken as the nominal 
strength S n , multiplied by the applicable strength 
reduction factor 0 . 

404.6.2 Structures and structural members shall have 
design strength at all sections, <f>S n , greater than or equal 
to the required strength U calculated for the factored 
loads and forces in such' combinations as required by this 
Section or the general building code. 

404.7 Serviceability 

404.7.1 Evaluation of performance at service load 
conditions shall consider reactions, moments, torsions, 
shears, and axial forces induced by prestressing, creep, 
shrinkage, temperature change, axial deformation, 
restraint of attached structural members, and foundation 
settlement. 

404.7.2 For structures, structural members, and their 
connections, the requirements of Section 404.7.1 shall be 
deemed to be satisfied if designed in accordance with the 
provisions of the applicable member sections. 

404.8 Durability 

404.8.1 Concrete mixtures shall be designed in 
accordance with the requirements of Sections 419.3.2 and 
426.4, considering applicable environmental exposure to 
provide required durability. 


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CHAPTER 4 - Structural Concrete 4-33 


404.8.2 Reinforcement shall be protected from 404.12 Requirements for Specific Types of 

corrosion in accordance with Section 420.6. Construction 


404.9 Sustainability 

404.9.1 The licensed design professional shall be 
permitted to specify in the construction documents 
sustainability requirements in addition to strength, 
serviceability, and durability requirements of this Code. 

404.9.2 The strength, serviceability, and durability 
requirements of this Code shall take precedence over 
sustainability considerations. 

404.10 Structural Integrity 

404.10.1 General 

404.10.1.1 Reinforcement and connections shall be 
detailed to tie the structure together effectively and to 
improve overall structural integrity. 

404.10.2 Minimum Requirements for Structural 
Integrity 

404.10.2.1 Structural members and their connections shall 
be in accordance with structural integrity requirements in 
Table 404.10.2.1. 


Table 404.10.2.1 

Minimum Requirements for Structural Integrity 


Member Type 

Section 

Non-prestressed two-way slabs 

408.7.4.2 

Prestressed two-way slabs 

408.7.5.6 

Non-prestressed two-way joist systems 

408.8.1.6 

Cast-in-place beams 

409.7.7 

Non-prestressed one-way joist systems 

409.8.1.6 

Precast joints and connections 

416.2.1.8 


404.11 Fire Resistance 

404.11.1 Structural concrete members shall satisfy the 
fire protection requirements of the general building code. 

404.11.2 Where the general building code requires a 
thickness of concrete cover for fire protection greater than 
the concrete cover specified in Section 420.6.1, such 
greater thickness shall govern. 


404.12.1 Precast Concrete Systems 

404.12.1 Design of precast concrete members and 
connections shall include loading and restraint conditions 
from initial fabrication to end use in the structure, 
including form removal, storage, transportation, and 
erection. 

404.12.1.2 Design, fabrication, and construction of 
precast members and their connections shall include the 
effects of tolerances. 

404.12.1.3 When precast members are incorporated into 
a structural system, the forces and deformations occurring 
in and adjacent to connections shall be included in the 
design. 

404.12.1.4 Where system behavior requires in-plane 
loads to be transferred between the members of a precast 
floor or wall system, (a) and (b) shall be satisfied: 

a. In-plane load paths shall be continuous through both 
connections and members. 

b. Where tension loads occur, a load path of steel or 
steel reinforcement, with or without splices, shall be 
provided. 

404.12.1.5 Distribution of forces that act perpendicular 
to the plane of precast members shall be established by 
analysis or test. 

404.12.2 Prestressed Concrete Systems 

404.12.2.1 Design of prestressed members and systems 
shall be based on strength and on behavior at service 
conditions at all critical stages during the life of the 
structure from the time prestress is first applied. 

404.12.2.2 Provisions shall be made for effects on 
adjoining construction of elastic and plastic deformations, 
deflections, changes in length, and rotations due to 
pre stressing. Effects of temperature change, restraint of 
attached structural members, foundation settlement, creep, 
and shrinkage shall also be considered. 

404.12.2.3 Stress concentrations due to prestressing 
shall be considered in design. 


404.12.2.4 Effect of loss of area due to open ducts shall 
be considered in computing section properties before 
grout in post-tensioning ducts has attained design 
strength. 


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4-34 CHAPTER 4 ~ Structural Concrete 


404.12.2.5 Post-tensioning tendons shall be permitted 
to be external to any concrete section of a member. 
Strength and serviceability design requirements of this 
Code shall be used to evaluate the effects of external 
tendon forces on the concrete structure. 

404.12.3 Composite Concrete Flexural Members 

404.12.3.1 This Chapter shall apply to composite 
concrete flexural members as defined in Section 402. 

404.12.3.2 Individual members shall be designed for all 
critical stages of loading. 

404.12.3.3 Members shall be designed to support all 
loads introduced prior to lull development of design 
strength of composite members. 

404.12.3.4 Reinforcement shall be detailed to minimize 
cracking and to prevent separation of individual 
components of composite members. 

404.12.4 Composite Steel and Concrete 
Construction 

404.12.4.1 Composite compression members shall 
include all members reinforced longitudinally with 
structural steel shapes, pipe, or tubing with or without 
longitudinal bars. 

404.12.4.1 The design of composite compression 
members shall be in accordance with Section 410. 

404.12.5 Structural Plain Concrete Systems 

404.12.5.1 The design of structural plain concrete 
members, both cast-in-place and precast, shall be in 
accordance with Section 414. 

404.13 Construction and Inspection 

404.13.1 Specifications for construction execution shall 
be in accordance with Section 426. 

404.13.2 Specifications for construction execution shall 
be in accordance with Section 426. 

404.14 Strength Evaluation of Existing Structures 

404.14.1 Strength evaluation of existing structures shall 
be in accordance with Section 427. 


SECTION 405 
LOADS 

405.1 Scope 

405.1.1 This Section shall apply to selection of load 
factors and combinations used in design, except as 
permitted in Section 427. 

405.2 General 

405.2.1 Loads shall include self-weight; applied loads; 
and effects of prestressing, earthquakes, restraint of 
volume change, and differential settlement. 

405.2.2 Loads and seismic zones shall be in 
accordance with the general building code, or determined 
by another authority having jurisdiction in areas without a 
legally adopted building code. 

405.2.3 Live load reductions shall be permitted in 
accordance with the general building code or, in the 
absence of a general building code, in accordance with 
ASCE/SEI 7. 

405.3 Load Factors and Combinations 

405.3.1 Required strength, 17, shall be at least equal to 
the effects of factored loads in Table 405.3.1, with 
exceptions and additions in Sections 405.3.3 through 
405.3.12. 


Table 405.3.1 Load Combinations 


Load Designation 

Equation 

Primary 

Load 

U= IAD 

(405.31a) 

D 

U= 1.2 D+ 1.6L + 0.5 (iror/v’) 

(405.31b) 

L 

U= 1.2 D+ 1.6 (Lr or R) 

+ (1.0Z, or 0.5 IK) 

(405.31c) 

Lr or R 

U= \.2D+\.W+ 1.0 L 
+ 0.5 (Lr or R) 

(405. 31d) 

W 

U= \.2D + 1.0£ + 1.0L 

(405.3 le) 

E 

[/ = 0.9 D+ 1.0 W 

(405. 3 If) 

W 

U = 0.9D + 1.0 £ 

(405.3 lg) 

E 


405.3.2 The effect of one or more loads not acting 
simultaneously shall be investigated. 


405.3.3 The load factor on live load L in Eqs. 405.3. lc, 
405.3. Id, and 405.3. le shall be permitted to be reduced to 
0.5 except for (a), (b), or (c): 


a. Garages; 

b. Areas occupied as places of public assembly; 


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CHAPTER 4 - Structural Concrete 


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c. Areas where L is greater than 4.8 kPa. 

405.3.4 If applicable, L shall include (a) through (f): 

a. Concentrated live loads; 

b. Vehicular loads; 

c. Crane loads; 

d. Loads on hand rails, guardrails, and vehicular 
barrier systems; 

e. Impact effects; 

f. Vibration effects. 

405.3.5 If wind load W is based on service-level loads, 
1.6 W shall be used in place of 1 .OW in Eqs. 405. 3. Id 
and 405.3. If, and 0 . 8 W shall be used in place of 0 . 5 W 
in Eq. 405.3.1c. 

405.3.6 The structural effects of forces due to restraint 
of volume change and differential settlement, T, shall be 
considered in combination with other loads if the effects 
of T can adversely affect structural safety or performance. 
The load factor for T shall be established con